diff --git a/wp-admin/admin.php b/wp-admin/admin.php
index a54ca21ba7..bbf00d5c87 100644
--- a/wp-admin/admin.php
+++ b/wp-admin/admin.php
@@ -175,7 +175,7 @@ if ( isset($plugin_page) ) {
 	if ( ! $page_hook = get_plugin_page_hook($plugin_page, $the_parent) ) {
 		$page_hook = get_plugin_page_hook($plugin_page, $plugin_page);
 
-		// Backwards compatibility for plugins using add_management_page().
+		// Back-compat for plugins using add_management_page().
 		if ( empty( $page_hook ) && 'edit.php' == $pagenow && '' != get_plugin_page_hook($plugin_page, 'tools.php') ) {
 			// There could be plugin specific params on the URL, so we need the whole query string
 			if ( !empty($_SERVER[ 'QUERY_STRING' ]) )
diff --git a/wp-admin/includes/ajax-actions.php b/wp-admin/includes/ajax-actions.php
index e3b345c53c..63a6cdadc3 100644
--- a/wp-admin/includes/ajax-actions.php
+++ b/wp-admin/includes/ajax-actions.php
@@ -2466,7 +2466,7 @@ function wp_ajax_save_attachment() {
 }
 
 /**
- * Ajax handler for saving backwards compatible attachment attributes.
+ * Ajax handler for saving backward compatible attachment attributes.
  *
  * @since 3.5.0
  */
@@ -2552,7 +2552,7 @@ function wp_ajax_save_attachment_order() {
  * Ajax handler for sending an attachment to the editor.
  *
  * Generates the HTML to send an attachment to the editor.
- * Backwards compatible with the media_send_to_editor filter
+ * Backward compatible with the media_send_to_editor filter
  * and the chain of filters that follow.
  *
  * @since 3.5.0
@@ -2617,7 +2617,7 @@ function wp_ajax_send_attachment_to_editor() {
  *
  * Generates the HTML to send a non-image embed link to the editor.
  *
- * Backwards compatible with the following filters:
+ * Backward compatible with the following filters:
  * - file_send_to_editor_url
  * - audio_send_to_editor_url
  * - video_send_to_editor_url
diff --git a/wp-admin/includes/class-wp-list-table.php b/wp-admin/includes/class-wp-list-table.php
index 2381751b87..32de015261 100644
--- a/wp-admin/includes/class-wp-list-table.php
+++ b/wp-admin/includes/class-wp-list-table.php
@@ -166,7 +166,7 @@ class WP_List_Table {
 	}
 
 	/**
-	 * Make private properties readable for backwards compatibility.
+	 * Make private properties readable for backward compatibility.
 	 *
 	 * @since 4.0.0
 	 * @access public
@@ -181,7 +181,7 @@ class WP_List_Table {
 	}
 
 	/**
-	 * Make private properties settable for backwards compatibility.
+	 * Make private properties settable for backward compatibility.
 	 *
 	 * @since 4.0.0
 	 * @access public
@@ -197,7 +197,7 @@ class WP_List_Table {
 	}
 
 	/**
-	 * Make private properties checkable for backwards compatibility.
+	 * Make private properties checkable for backward compatibility.
 	 *
 	 * @since 4.0.0
 	 * @access public
@@ -212,7 +212,7 @@ class WP_List_Table {
 	}
 
 	/**
-	 * Make private properties un-settable for backwards compatibility.
+	 * Make private properties un-settable for backward compatibility.
 	 *
 	 * @since 4.0.0
 	 * @access public
@@ -226,7 +226,7 @@ class WP_List_Table {
 	}
 
 	/**
-	 * Make private/protected methods readable for backwards compatibility.
+	 * Make private/protected methods readable for backward compatibility.
 	 *
 	 * @since 4.0.0
 	 * @access public
@@ -432,7 +432,7 @@ class WP_List_Table {
 	 * @access protected
 	 *
 	 * @param string $which The location of the bulk actions: 'top' or 'bottom'.
-	 *                      This is designated as optional for backwards-compatibility.
+	 *                      This is designated as optional for backward compatibility.
 	 */
 	protected function bulk_actions( $which = '' ) {
 		if ( is_null( $this->_actions ) ) {
diff --git a/wp-admin/includes/class-wp-screen.php b/wp-admin/includes/class-wp-screen.php
index ebd20b895a..77589fe400 100644
--- a/wp-admin/includes/class-wp-screen.php
+++ b/wp-admin/includes/class-wp-screen.php
@@ -418,9 +418,7 @@ final class WP_Screen {
 	}
 
 	/**
-	 * Sets the old string-based contextual help for the screen.
-	 *
-	 * For backwards compatibility.
+	 * Sets the old string-based contextual help for the screen for backward compatibility.
 	 *
 	 * @since 3.3.0
 	 *
@@ -722,7 +720,7 @@ final class WP_Screen {
 	/**
 	 * Render the screen's help section.
 	 *
-	 * This will trigger the deprecated filters for backwards compatibility.
+	 * This will trigger the deprecated filters for backward compatibility.
 	 *
 	 * @since 3.3.0
 	 *
diff --git a/wp-admin/includes/plugin.php b/wp-admin/includes/plugin.php
index 3b29bd1af9..b6fe335fe7 100644
--- a/wp-admin/includes/plugin.php
+++ b/wp-admin/includes/plugin.php
@@ -487,7 +487,7 @@ function is_plugin_active_for_network( $plugin ) {
  * be activated only as a network wide plugin. The plugin would also work
  * when Multisite is not enabled.
  *
- * Checks for "Site Wide Only: true" for backwards compatibility.
+ * Checks for "Site Wide Only: true" for backward compatibility.
  *
  * @since 3.0.0
  *
diff --git a/wp-admin/js/common.js b/wp-admin/js/common.js
index 9cd1fff910..6f8d1df4ca 100644
--- a/wp-admin/js/common.js
+++ b/wp-admin/js/common.js
@@ -394,7 +394,7 @@ $document.ready( function() {
 	}
 
 	/*
-	 * The `.below-h2` class is here just for backwards compatibility with plugins
+	 * The `.below-h2` class is here just for backward compatibility with plugins
 	 * that are (incorrectly) using it. Do not use. Use `.inline` instead. See #34570.
 	 */
 	$( 'div.updated, div.error, div.notice' ).not( '.inline, .below-h2' ).insertAfter( $( '.wrap h1, .wrap h2' ).first() );
diff --git a/wp-admin/js/password-strength-meter.js b/wp-admin/js/password-strength-meter.js
index a075c269f8..2ac7e86c83 100644
--- a/wp-admin/js/password-strength-meter.js
+++ b/wp-admin/js/password-strength-meter.js
@@ -70,6 +70,6 @@ var passwordStrength;
 		}
 	};
 
-	// Backwards compatibility.
+	// Back-compat.
 	passwordStrength = wp.passwordStrength.meter;
-})(jQuery);
\ No newline at end of file
+})(jQuery);
diff --git a/wp-admin/js/wp-fullscreen-stub.js b/wp-admin/js/wp-fullscreen-stub.js
index c31c7eec99..df5d2e7c96 100644
--- a/wp-admin/js/wp-fullscreen-stub.js
+++ b/wp-admin/js/wp-fullscreen-stub.js
@@ -1,5 +1,5 @@
 /**
- * Distraction-Free Writing (wp-fullscreen) backwards compatibility stub.
+ * Distraction-Free Writing (wp-fullscreen) backward compatibility stub.
  * Todo: remove at the end of 2016.
  *
  * Original was deprecated in 4.1, removed in 4.3.
diff --git a/wp-admin/menu.php b/wp-admin/menu.php
index f85ebd3ab6..6c0b38f723 100644
--- a/wp-admin/menu.php
+++ b/wp-admin/menu.php
@@ -265,7 +265,7 @@ $_wp_real_parent_file['page-new.php'] = 'edit.php?post_type=page';
 $_wp_real_parent_file['wpmu-admin.php'] = 'tools.php';
 $_wp_real_parent_file['ms-admin.php'] = 'tools.php';
 
-// ensure we're backwards compatible
+// Ensure backward compatibility.
 $compat = array(
 	'index' => 'dashboard',
 	'edit' => 'posts',
diff --git a/wp-admin/options-head.php b/wp-admin/options-head.php
index 1c706c87d7..bee3ae7e67 100644
--- a/wp-admin/options-head.php
+++ b/wp-admin/options-head.php
@@ -11,7 +11,7 @@
 wp_reset_vars( array( 'action' ) );
 
 if ( isset( $_GET['updated'] ) && isset( $_GET['page'] ) ) {
-	// For backwards compat with plugins that don't use the Settings API and just set updated=1 in the redirect
+	// For back-compat with plugins that don't use the Settings API and just set updated=1 in the redirect.
 	add_settings_error('general', 'settings_updated', __('Settings saved.'), 'updated');
 }
 
diff --git a/wp-admin/theme-install.php b/wp-admin/theme-install.php
index 9d495eaab3..3f85cc632f 100644
--- a/wp-admin/theme-install.php
+++ b/wp-admin/theme-install.php
@@ -118,8 +118,7 @@ include(ABSPATH . 'wp-admin/admin-header.php');
 	/**
 	 * Filter the tabs shown on the Add Themes screen.
 	 *
-	 * This filter is for backwards compatibility only, for the suppression
-	 * of the upload tab.
+	 * This filter is for backward compatibility only, for the suppression of the upload tab.
 	 *
 	 * @since 2.8.0
 	 *
diff --git a/wp-includes/author-template.php b/wp-includes/author-template.php
index ba609ab275..eefcf27850 100644
--- a/wp-includes/author-template.php
+++ b/wp-includes/author-template.php
@@ -45,7 +45,7 @@ function get_the_author($deprecated = '') {
  * still use the old behavior will also pass the value from get_the_author().
  *
  * The normal, expected behavior of this function is to echo the author and not
- * return it. However, backwards compatibility has to be maintained.
+ * return it. However, backward compatibility has to be maintained.
  *
  * @since 0.71
  * @see get_the_author()
diff --git a/wp-includes/cache.php b/wp-includes/cache.php
index fc4a257606..10fa610569 100644
--- a/wp-includes/cache.php
+++ b/wp-includes/cache.php
@@ -344,7 +344,7 @@ class WP_Object_Cache {
 	private $multisite;
 
 	/**
-	 * Makes private properties readable for backwards compatibility.
+	 * Makes private properties readable for backward compatibility.
 	 *
 	 * @since 4.0.0
 	 * @access public
@@ -357,7 +357,7 @@ class WP_Object_Cache {
 	}
 
 	/**
-	 * Makes private properties settable for backwards compatibility.
+	 * Makes private properties settable for backward compatibility.
 	 *
 	 * @since 4.0.0
 	 * @access public
@@ -371,7 +371,7 @@ class WP_Object_Cache {
 	}
 
 	/**
-	 * Makes private properties checkable for backwards compatibility.
+	 * Makes private properties checkable for backward compatibility.
 	 *
 	 * @since 4.0.0
 	 * @access public
@@ -384,7 +384,7 @@ class WP_Object_Cache {
 	}
 
 	/**
-	 * Makes private properties un-settable for backwards compatibility.
+	 * Makes private properties un-settable for backward compatibility.
 	 *
 	 * @since 4.0.0
 	 * @access public
diff --git a/wp-includes/category.php b/wp-includes/category.php
index d2440e962b..93d9b59956 100644
--- a/wp-includes/category.php
+++ b/wp-includes/category.php
@@ -10,7 +10,7 @@
  * Retrieve list of category objects.
  *
  * If you change the type to 'link' in the arguments, then the link categories
- * will be returned instead. Also all categories will be updated to be backwards
+ * will be returned instead. Also all categories will be updated to be backward
  * compatible with pre-2.3 plugins and themes.
  *
  * @since 2.1.0
@@ -77,7 +77,7 @@ function get_categories( $args = '' ) {
  * If you look at get_term(), then both types will be passed through several
  * filters and finally sanitized based on the $filter parameter value.
  *
- * The category will converted to maintain backwards compatibility.
+ * The category will converted to maintain backward compatibility.
  *
  * @since 1.5.1
  *
diff --git a/wp-includes/certificates/ca-bundle.crt b/wp-includes/certificates/ca-bundle.crt
index 6031cc6a87..2ae3a97f4f 100644
--- a/wp-includes/certificates/ca-bundle.crt
+++ b/wp-includes/certificates/ca-bundle.crt
@@ -3,7 +3,7 @@
 ##
 ## Certificate data from Mozilla as of: Wed Sep 16 08:58:11 2015
 ## Includes a WordPress Modification - We include the 'legacy' 1024bit certificates
-## for backwards compatibility. See https://core.trac.wordpress.org/ticket/34935#comment:10
+## for backward compatibility. See https://core.trac.wordpress.org/ticket/34935#comment:10
 ##
 ## This is a bundle of X.509 certificates of public Certificate Authorities
 ## (CA). These were automatically extracted from Mozilla's root certificates
diff --git a/wp-includes/class-oembed.php b/wp-includes/class-oembed.php
index 909524bc30..fe222518d8 100644
--- a/wp-includes/class-oembed.php
+++ b/wp-includes/class-oembed.php
@@ -38,7 +38,7 @@ class WP_oEmbed {
 	public static $early_providers = array();
 
 	/**
-	 * A list of private/protected methods, used for backwards compatibility.
+	 * A list of private/protected methods, used for backward compatibility.
 	 *
 	 * @since 4.2.0
 	 * @access private
@@ -192,7 +192,7 @@ class WP_oEmbed {
 	}
 
 	/**
-	 * Exposes private/protected methods for backwards compatibility.
+	 * Exposes private/protected methods for backward compatibility.
 	 *
 	 * @since 4.0.0
 	 * @access public
diff --git a/wp-includes/class-wp-comment-query.php b/wp-includes/class-wp-comment-query.php
index bdb750c025..190bc2d764 100644
--- a/wp-includes/class-wp-comment-query.php
+++ b/wp-includes/class-wp-comment-query.php
@@ -125,7 +125,7 @@ class WP_Comment_Query {
 	public $max_num_pages = 0;
 
 	/**
-	 * Make private/protected methods readable for backwards compatibility.
+	 * Make private/protected methods readable for backward compatibility.
 	 *
 	 * @since 4.0.0
 	 * @access public
diff --git a/wp-includes/class-wp-editor.php b/wp-includes/class-wp-editor.php
index bfbc547acf..4c0827a3ec 100644
--- a/wp-includes/class-wp-editor.php
+++ b/wp-includes/class-wp-editor.php
@@ -54,7 +54,8 @@ final class _WP_Editors {
 	 *     @type string     $editor_class      Extra classes to add to the editor textarea element. Default empty.
 	 *     @type bool       $teeny             Whether to output the minimal editor config. Examples include
 	 *                                         Press This and the Comment editor. Default false.
-	 *     @type bool       $dfw               Deprecated in 4.1. Since 4.3 used only to enqueue wp-fullscreen-stub.js for backwards compatibility.
+	 *     @type bool       $dfw               Deprecated in 4.1. Since 4.3 used only to enqueue wp-fullscreen-stub.js
+	 *                                         for backward compatibility.
 	 *     @type bool|array $tinymce           Whether to load TinyMCE. Can be used to pass settings directly to
 	 *                                         TinyMCE using an array. Default true.
 	 *     @type bool|array $quicktags         Whether to load Quicktags. Can be used to pass settings directly to
diff --git a/wp-includes/class-wp-http-requests-response.php b/wp-includes/class-wp-http-requests-response.php
index 981756af01..d85dffc7e8 100644
--- a/wp-includes/class-wp-http-requests-response.php
+++ b/wp-includes/class-wp-http-requests-response.php
@@ -144,7 +144,7 @@ class WP_HTTP_Requests_Response extends WP_HTTP_Response implements ArrayAccess
 	/**
 	 * Check if an ArrayAccess offset exists.
 	 *
-	 * This is for backwards compatibility for array access.
+	 * This is for array access back-compat.
 	 *
 	 * @param string|int $key Array offset.
 	 * @return bool True if the offset exists, false otherwise.
@@ -157,7 +157,7 @@ class WP_HTTP_Requests_Response extends WP_HTTP_Response implements ArrayAccess
 	/**
 	 * Get an ArrayAccess value.
 	 *
-	 * This is for backwards compatibility for array access.
+	 * This is for array access back-compat.
 	 *
 	 * @param string|int $key Array offset to get.
 	 * @return mixed Value if the key is a valid offset, null if invalid.
@@ -189,7 +189,7 @@ class WP_HTTP_Requests_Response extends WP_HTTP_Response implements ArrayAccess
 	/**
 	 * Set an ArrayAccess value.
 	 *
-	 * This is for backwards compatibility for array access.
+	 * This is for array access back-compat.
 	 *
 	 * @param string|int $key Array offset to set.
 	 * @param mixed $value Value to set.
@@ -219,7 +219,7 @@ class WP_HTTP_Requests_Response extends WP_HTTP_Response implements ArrayAccess
 	/**
 	 * Unset an ArrayAccess value.
 	 *
-	 * This is for backwards compatibility for array access.
+	 * This is for array access back-compat.
 	 *
 	 * @param string|int $key Array offset to remove.
 	 */
diff --git a/wp-includes/class-wp-http-streams.php b/wp-includes/class-wp-http-streams.php
index 80f30a4324..3620446a96 100644
--- a/wp-includes/class-wp-http-streams.php
+++ b/wp-includes/class-wp-http-streams.php
@@ -415,7 +415,7 @@ class WP_Http_Streams {
 /**
  * Deprecated HTTP Transport method which used fsockopen.
  *
- * This class is not used, and is included for backwards compatibility only.
+ * This class is not used, and is included for backward compatibility only.
  * All code should make use of WP_Http directly through its API.
  *
  * @see WP_HTTP::request
@@ -424,5 +424,5 @@ class WP_Http_Streams {
  * @deprecated 3.7.0 Please use WP_HTTP::request() directly
  */
 class WP_HTTP_Fsockopen extends WP_HTTP_Streams {
-	// For backwards compatibility for users who are using the class directly.
+	// For backward compatibility for users who are using the class directly.
 }
diff --git a/wp-includes/class-wp-image-editor-imagick.php b/wp-includes/class-wp-image-editor-imagick.php
index 74ba793be7..bbc9fa85a1 100644
--- a/wp-includes/class-wp-image-editor-imagick.php
+++ b/wp-includes/class-wp-image-editor-imagick.php
@@ -343,7 +343,7 @@ class WP_Image_Editor_Imagick extends WP_Image_Editor {
 			 * Use resizeImage() when it's available and a valid filter value is set.
 			 * Otherwise, fall back to the scaleImage() method for resizing, which
 			 * results in better image quality over resizeImage() with default filter
-			 * settings and retains backwards compatibility with pre 4.5 functionality.
+			 * settings and retains backward compatibility with pre 4.5 functionality.
 			 */
 			if ( is_callable( array( $this->image, 'resizeImage' ) ) && $filter ) {
 				$this->image->setOption( 'filter:support', '2.0' );
diff --git a/wp-includes/class-wp-image-editor.php b/wp-includes/class-wp-image-editor.php
index 5b6f4ac9a0..44fd66f00c 100644
--- a/wp-includes/class-wp-image-editor.php
+++ b/wp-includes/class-wp-image-editor.php
@@ -276,7 +276,7 @@ abstract class WP_Image_Editor {
 			}
 		}
 
-		// Allow 0, but squash to 1 due to identical images in GD, and for backwards compatibility.
+		// Allow 0, but squash to 1 due to identical images in GD, and for backward compatibility.
 		if ( 0 === $quality ) {
 			$quality = 1;
 		}
diff --git a/wp-includes/class-wp-rewrite.php b/wp-includes/class-wp-rewrite.php
index 7c621fb001..9c8b492c8f 100644
--- a/wp-includes/class-wp-rewrite.php
+++ b/wp-includes/class-wp-rewrite.php
@@ -1743,7 +1743,7 @@ class WP_Rewrite {
 	 * }
 	 */
 	public function add_permastruct( $name, $struct, $args = array() ) {
-		// Backwards compatibility for the old parameters: $with_front and $ep_mask.
+		// Back-compat for the old parameters: $with_front and $ep_mask.
 		if ( ! is_array( $args ) )
 			$args = array( 'with_front' => $args );
 		if ( func_num_args() == 4 )
diff --git a/wp-includes/class-wp-roles.php b/wp-includes/class-wp-roles.php
index 94fc672613..ff733e2206 100644
--- a/wp-includes/class-wp-roles.php
+++ b/wp-includes/class-wp-roles.php
@@ -79,7 +79,7 @@ class WP_Roles {
 	}
 
 	/**
-	 * Make private/protected methods readable for backwards compatibility.
+	 * Make private/protected methods readable for backward compatibility.
 	 *
 	 * @since 4.0.0
 	 * @access public
diff --git a/wp-includes/class-wp-theme.php b/wp-includes/class-wp-theme.php
index ad3b1ec242..8c1134fd18 100644
--- a/wp-includes/class-wp-theme.php
+++ b/wp-includes/class-wp-theme.php
@@ -447,8 +447,10 @@ final class WP_Theme implements ArrayAccess {
 		switch ( $offset ) {
 			case 'Name' :
 			case 'Title' :
-				// See note above about using translated data. get() is not ideal.
-				// It is only for backwards compatibility. Use display().
+				/*
+				 * See note above about using translated data. get() is not ideal.
+				 * It is only for backward compatibility. Use display().
+				 */
 				return $this->get('Name');
 			case 'Author' :
 				return $this->display( 'Author');
diff --git a/wp-includes/class-wp-user-query.php b/wp-includes/class-wp-user-query.php
index 1fdbd03c37..a8dcd44ccd 100644
--- a/wp-includes/class-wp-user-query.php
+++ b/wp-includes/class-wp-user-query.php
@@ -736,7 +736,7 @@ class WP_User_Query {
 	}
 
 	/**
-	 * Make private properties readable for backwards compatibility.
+	 * Make private properties readable for backward compatibility.
 	 *
 	 * @since 4.0.0
 	 * @access public
@@ -751,7 +751,7 @@ class WP_User_Query {
 	}
 
 	/**
-	 * Make private properties settable for backwards compatibility.
+	 * Make private properties settable for backward compatibility.
 	 *
 	 * @since 4.0.0
 	 * @access public
@@ -767,7 +767,7 @@ class WP_User_Query {
 	}
 
 	/**
-	 * Make private properties checkable for backwards compatibility.
+	 * Make private properties checkable for backward compatibility.
 	 *
 	 * @since 4.0.0
 	 * @access public
@@ -782,7 +782,7 @@ class WP_User_Query {
 	}
 
 	/**
-	 * Make private properties un-settable for backwards compatibility.
+	 * Make private properties un-settable for backward compatibility.
 	 *
 	 * @since 4.0.0
 	 * @access public
@@ -796,7 +796,7 @@ class WP_User_Query {
 	}
 
 	/**
-	 * Make private/protected methods readable for backwards compatibility.
+	 * Make private/protected methods readable for backward compatibility.
 	 *
 	 * @since 4.0.0
 	 * @access public
diff --git a/wp-includes/class-wp-user.php b/wp-includes/class-wp-user.php
index 210919d6e4..c0c42166af 100644
--- a/wp-includes/class-wp-user.php
+++ b/wp-includes/class-wp-user.php
@@ -242,7 +242,7 @@ class WP_User {
 	}
 
 	/**
-	 * Makes private/protected methods readable for backwards compatibility.
+	 * Makes private/protected methods readable for backward compatibility.
 	 *
 	 * @since 4.3.0
 	 * @access public
diff --git a/wp-includes/class-wp-walker.php b/wp-includes/class-wp-walker.php
index ee68a205e9..57bd90bfd3 100644
--- a/wp-includes/class-wp-walker.php
+++ b/wp-includes/class-wp-walker.php
@@ -139,7 +139,7 @@ class Walker {
 		//display this element
 		$this->has_children = ! empty( $children_elements[ $id ] );
 		if ( isset( $args[0] ) && is_array( $args[0] ) ) {
-			$args[0]['has_children'] = $this->has_children; // Backwards compatibility.
+			$args[0]['has_children'] = $this->has_children; // Back-compat.
 		}
 
 		$cb_args = array_merge( array(&$output, $element, $depth), $args);
@@ -386,7 +386,7 @@ class Walker {
 	 *
 	 * @since 2.7.0
 	 * @access public
-	 * 
+	 *
 	 * @param array $elements Elements to list.
 	 * @return int Number of root elements.
 	 */
diff --git a/wp-includes/class-wp-xmlrpc-server.php b/wp-includes/class-wp-xmlrpc-server.php
index 531dd50c9e..dd51eca718 100644
--- a/wp-includes/class-wp-xmlrpc-server.php
+++ b/wp-includes/class-wp-xmlrpc-server.php
@@ -171,7 +171,7 @@ class wp_xmlrpc_server extends IXR_Server {
 	}
 
 	/**
-	 * Make private/protected methods readable for backwards compatibility.
+	 * Make private/protected methods readable for backward compatibility.
 	 *
 	 * @since 4.0.0
 	 * @access public
diff --git a/wp-includes/comment-template.php b/wp-includes/comment-template.php
index 8416cea9ac..86abee5443 100644
--- a/wp-includes/comment-template.php
+++ b/wp-includes/comment-template.php
@@ -704,7 +704,7 @@ function get_comment_link( $comment = null, $args = array() ) {
 
 	$comment = get_comment($comment);
 
-	// Backwards compat
+	// Back-compat.
 	if ( ! is_array( $args ) ) {
 		$args = array( 'page' => $args );
 	}
diff --git a/wp-includes/css/buttons-rtl.css b/wp-includes/css/buttons-rtl.css
index 05843d53cd..0b6bff7934 100644
--- a/wp-includes/css/buttons-rtl.css
+++ b/wp-includes/css/buttons-rtl.css
@@ -8,7 +8,7 @@ buttons in the following files are updated.
 
 WordPress-style Buttons
 =======================
-Create a button by adding the `.button` class to an element. For backwards
+Create a button by adding the `.button` class to an element. For backward
 compatibility, we support several other classes (such as `.button-secondary`),
 but these will *not* work with the stackable classes described below.
 
diff --git a/wp-includes/css/buttons.css b/wp-includes/css/buttons.css
index 17bf3a769c..6ea9964eb2 100644
--- a/wp-includes/css/buttons.css
+++ b/wp-includes/css/buttons.css
@@ -8,7 +8,7 @@ buttons in the following files are updated.
 
 WordPress-style Buttons
 =======================
-Create a button by adding the `.button` class to an element. For backwards
+Create a button by adding the `.button` class to an element. For backward
 compatibility, we support several other classes (such as `.button-secondary`),
 but these will *not* work with the stackable classes described below.
 
diff --git a/wp-includes/deprecated.php b/wp-includes/deprecated.php
index f79761ba26..7bb13bcd36 100644
--- a/wp-includes/deprecated.php
+++ b/wp-includes/deprecated.php
@@ -2061,7 +2061,7 @@ function js_escape( $text ) {
  */
 function wp_specialchars( $string, $quote_style = ENT_NOQUOTES, $charset = false, $double_encode = false ) {
 	_deprecated_function( __FUNCTION__, '2.8', 'esc_html()' );
-	if ( func_num_args() > 1 ) { // Maintain backwards compat for people passing additional args
+	if ( func_num_args() > 1 ) { // Maintain back-compat for people passing additional arguments.
 		$args = func_get_args();
 		return call_user_func_array( '_wp_specialchars', $args );
 	} else {
@@ -2085,14 +2085,14 @@ function attribute_escape( $text ) {
 }
 
 /**
- * Register widget for sidebar with backwards compatibility.
+ * Register widget for sidebar with backward compatibility.
  *
  * Allows $name to be an array that accepts either three elements to grab the
  * first element and the third for the name or just uses the first element of
  * the array for the name.
  *
- * Passes to {@link wp_register_sidebar_widget()} after argument list and
- * backwards compatibility is complete.
+ * Passes to wp_register_sidebar_widget() after argument list and backward
+ * compatibility is complete.
  *
  * @since 2.2.0
  * @deprecated 2.8.0 Use wp_register_sidebar_widget()
diff --git a/wp-includes/formatting.php b/wp-includes/formatting.php
index f58e435fc1..27ac8db3cb 100644
--- a/wp-includes/formatting.php
+++ b/wp-includes/formatting.php
@@ -934,7 +934,7 @@ function _wp_specialchars( $string, $quote_style = ENT_NOQUOTES, $charset = fals
 
 	$string = @htmlspecialchars( $string, $quote_style, $charset, $double_encode );
 
-	// Backwards compatibility
+	// Back-compat.
 	if ( 'single' === $_quote_style )
 		$string = str_replace( "'", ''', $string );
 
diff --git a/wp-includes/functions.php b/wp-includes/functions.php
index d4731c0ab1..50bd8109b6 100644
--- a/wp-includes/functions.php
+++ b/wp-includes/functions.php
@@ -1849,7 +1849,8 @@ function wp_get_upload_dir() {
  * @uses _wp_upload_dir()
  *
  * @param string $time Optional. Time formatted in 'yyyy/mm'. Default null.
- * @param bool   $create_dir Optional. Whether to check and create the uploads directory. Default true (backwards compatible).
+ * @param bool   $create_dir Optional. Whether to check and create the uploads directory.
+ *                           Default true for backward compatibility.
  * @param bool   $refresh_cache Optional. Whether to refresh the cache. Default false.
  * @return array See above for description.
  */
diff --git a/wp-includes/general-template.php b/wp-includes/general-template.php
index fc7058a491..95b2636ce0 100644
--- a/wp-includes/general-template.php
+++ b/wp-includes/general-template.php
@@ -1074,7 +1074,7 @@ function _wp_render_title_tag() {
  * or the page title. However, it is mostly common sense to have the blog title
  * to the right with most browsers supporting tabs. You can achieve this by
  * using the seplocation parameter and setting the value to 'right'. This change
- * was introduced around 2.5.0, in case backwards compatibility of themes is
+ * was introduced around 2.5.0, in case backward compatibility of themes is
  * important.
  *
  * @since 1.0.0
diff --git a/wp-includes/js/wp-util.js b/wp-includes/js/wp-util.js
index 84cb5510bb..24991d0b02 100644
--- a/wp-includes/js/wp-util.js
+++ b/wp-includes/js/wp-util.js
@@ -96,8 +96,7 @@ window.wp = window.wp || {};
 
 				// Use with PHP's wp_send_json_success() and wp_send_json_error()
 				deferred.jqXHR = $.ajax( options ).done( function( response ) {
-					// Treat a response of `1` as successful for backwards
-					// compatibility with existing handlers.
+					// Treat a response of 1 as successful for backward compatibility with existing handlers.
 					if ( response === '1' || response === 1 )
 						response = { success: true };
 
diff --git a/wp-includes/load.php b/wp-includes/load.php
index 780613f574..b03bb98800 100644
--- a/wp-includes/load.php
+++ b/wp-includes/load.php
@@ -331,7 +331,7 @@ function wp_set_lang_dir() {
 			 */
 			define( 'WP_LANG_DIR', WP_CONTENT_DIR . '/languages' );
 			if ( !defined( 'LANGDIR' ) ) {
-				// Old static relative path maintained for limited backwards compatibility - won't work in some cases
+				// Old static relative path maintained for limited backward compatibility - won't work in some cases.
 				define( 'LANGDIR', 'wp-content/languages' );
 			}
 		} else {
@@ -344,7 +344,7 @@ function wp_set_lang_dir() {
 			 */
 			define( 'WP_LANG_DIR', ABSPATH . WPINC . '/languages' );
 			if ( !defined( 'LANGDIR' ) ) {
-				// Old relative path maintained for backwards compatibility
+				// Old relative path maintained for backward compatibility.
 				define( 'LANGDIR', WPINC . '/languages' );
 			}
 		}
diff --git a/wp-includes/locale.php b/wp-includes/locale.php
index cfca86e8a1..d7e370116d 100644
--- a/wp-includes/locale.php
+++ b/wp-includes/locale.php
@@ -332,9 +332,11 @@ class WP_Locale {
 	}
 
 	/**
-	 * Global variables are deprecated. For backwards compatibility only.
+	 * Global variables are deprecated.
 	 *
-	 * @deprecated For backwards compatibility only.
+	 * For backward compatibility only.
+	 *
+	 * @deprecated For backward compatibility only.
 	 * @access private
 	 *
 	 * @global array $weekday
diff --git a/wp-includes/query.php b/wp-includes/query.php
index 986b04001b..02bfba7748 100644
--- a/wp-includes/query.php
+++ b/wp-includes/query.php
@@ -4123,7 +4123,7 @@ class WP_Query {
 	}
 
 	/**
-	 * Make private properties readable for backwards compatibility.
+	 * Make private properties readable for backward compatibility.
 	 *
 	 * @since 4.0.0
 	 * @access public
@@ -4138,7 +4138,7 @@ class WP_Query {
 	}
 
 	/**
-	 * Make private properties checkable for backwards compatibility.
+	 * Make private properties checkable for backward compatibility.
 	 *
 	 * @since 4.0.0
 	 * @access public
@@ -4153,7 +4153,7 @@ class WP_Query {
 	}
 
 	/**
-	 * Make private/protected methods readable for backwards compatibility.
+	 * Make private/protected methods readable for backward compatibility.
 	 *
 	 * @since 4.0.0
 	 * @access public
diff --git a/wp-includes/rest-api/class-wp-rest-response.php b/wp-includes/rest-api/class-wp-rest-response.php
index 4acc8b634d..2c2a2825e0 100644
--- a/wp-includes/rest-api/class-wp-rest-response.php
+++ b/wp-includes/rest-api/class-wp-rest-response.php
@@ -293,7 +293,7 @@ class WP_REST_Response extends WP_HTTP_Response {
 		 *
 		 * Well-behaved clients should expand and normalise these back to their
 		 * full URI relation, however some naive clients may not resolve these
-		 * correctly, so adding new CURIEs may break backwards compatibility.
+		 * correctly, so adding new CURIEs may break backward compatibility.
 		 *
 		 * @since 4.5.0
 		 *
diff --git a/wp-includes/rewrite.php b/wp-includes/rewrite.php
index 0763dc500e..a96d773697 100644
--- a/wp-includes/rewrite.php
+++ b/wp-includes/rewrite.php
@@ -202,7 +202,7 @@ function remove_rewrite_tag( $tag ) {
 function add_permastruct( $name, $struct, $args = array() ) {
 	global $wp_rewrite;
 
-	// backwards compatibility for the old parameters: $with_front and $ep_mask
+	// Back-compat for the old parameters: $with_front and $ep_mask.
 	if ( ! is_array( $args ) )
 		$args = array( 'with_front' => $args );
 	if ( func_num_args() == 4 )
diff --git a/wp-includes/taxonomy.php b/wp-includes/taxonomy.php
index 7bc2d4018c..aa19e3549f 100644
--- a/wp-includes/taxonomy.php
+++ b/wp-includes/taxonomy.php
@@ -14,7 +14,7 @@
  * Creates the initial taxonomies.
  *
  * This function fires twice: in wp-settings.php before plugins are loaded (for
- * backwards compatibility reasons), and again on the {@see 'init'} action. We must
+ * backward compatibility reasons), and again on the {@see 'init'} action. We must
  * avoid registering rewrite rules before the {@see 'init'} action.
  *
  * @since 2.8.0
@@ -2197,7 +2197,7 @@ function wp_count_terms( $taxonomy, $args = array() ) {
 	$defaults = array('hide_empty' => false);
 	$args = wp_parse_args($args, $defaults);
 
-	// backwards compatibility
+	// backward compatibility
 	if ( isset($args['ignore_empty']) ) {
 		$args['hide_empty'] = $args['ignore_empty'];
 		unset($args['ignore_empty']);
diff --git a/wp-includes/theme-compat/comments.php b/wp-includes/theme-compat/comments.php
index 2e8ebc3ed3..c01b4f67d2 100644
--- a/wp-includes/theme-compat/comments.php
+++ b/wp-includes/theme-compat/comments.php
@@ -4,7 +4,7 @@
  * @subpackage Theme_Compat
  * @deprecated 3.0
  *
- * This file is here for Backwards compatibility with old themes and will be removed in a future version
+ * This file is here for backward compatibility with old themes and will be removed in a future version
  *
  */
 _deprecated_file(
diff --git a/wp-includes/theme-compat/footer.php b/wp-includes/theme-compat/footer.php
index 61f91b19dc..cd6b1873a8 100644
--- a/wp-includes/theme-compat/footer.php
+++ b/wp-includes/theme-compat/footer.php
@@ -4,8 +4,7 @@
  * @subpackage Theme_Compat
  * @deprecated 3.0
  *
- * This file is here for Backwards compatibility with old themes and will be removed in a future version
- *
+ * This file is here for backward compatibility with old themes and will be removed in a future version
  */
 _deprecated_file(
 	/* translators: %s: template name */
diff --git a/wp-includes/theme-compat/header.php b/wp-includes/theme-compat/header.php
index 432ae5b01f..8a6836892a 100644
--- a/wp-includes/theme-compat/header.php
+++ b/wp-includes/theme-compat/header.php
@@ -4,8 +4,7 @@
  * @subpackage Theme_Compat
  * @deprecated 3.0
  *
- * This file is here for Backwards compatibility with old themes and will be removed in a future version
- *
+ * This file is here for backward compatibility with old themes and will be removed in a future version.
  */
 _deprecated_file(
 	/* translators: %s: template name */
diff --git a/wp-includes/theme-compat/sidebar.php b/wp-includes/theme-compat/sidebar.php
index 23fa630328..3b2f9f08ba 100644
--- a/wp-includes/theme-compat/sidebar.php
+++ b/wp-includes/theme-compat/sidebar.php
@@ -4,8 +4,7 @@
  * @subpackage Theme_Compat
  * @deprecated 3.0
  *
- * This file is here for Backwards compatibility with old themes and will be removed in a future version
- *
+ * This file is here for backward compatibility with old themes and will be removed in a future version.
  */
 _deprecated_file(
 	/* translators: %s: template name */
diff --git a/wp-includes/theme.php b/wp-includes/theme.php
index dee0af6817..52bca79361 100644
--- a/wp-includes/theme.php
+++ b/wp-includes/theme.php
@@ -664,7 +664,7 @@ function locale_stylesheet() {
  * Switches the theme.
  *
  * Accepts one argument: $stylesheet of the theme. It also accepts an additional function signature
- * of two arguments: $template then $stylesheet. This is for backwards compatibility.
+ * of two arguments: $template then $stylesheet. This is for backward compatibility.
  *
  * @since 2.5.0
  *
@@ -1634,7 +1634,7 @@ function add_theme_support( $feature ) {
 			// the constant is always accurate (and is not defined later,  overriding our value).
 			// As stated above, the first value wins.
 			// Once we get to wp_loaded (just-in-time), define any constants we haven't already.
-			// Constants are lame. Don't reference them. This is just for backwards compatibility.
+			// Constants are lame. Don't reference them. This is just for backward compatibility.
 
 			if ( defined( 'NO_HEADER_TEXT' ) )
 				$args[0]['header-text'] = ! NO_HEADER_TEXT;
diff --git a/wp-includes/version.php b/wp-includes/version.php
index c0195b2b58..cd1658afd4 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.6-alpha-37430';
+$wp_version = '4.6-alpha-37431';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.
diff --git a/wp-includes/wp-db.php b/wp-includes/wp-db.php
index c2e576ced2..e05999ea06 100644
--- a/wp-includes/wp-db.php
+++ b/wp-includes/wp-db.php
@@ -685,7 +685,7 @@ class wpdb {
 	}
 
 	/**
-	 * Magic function, for backwards compatibility.
+	 * Magic function, for backward compatibility.
 	 *
 	 * @since 3.5.0
 	 *
@@ -705,7 +705,7 @@ class wpdb {
 	}
 
 	/**
-	 * Magic function, for backwards compatibility.
+	 * Magic function, for backward compatibility.
 	 *
 	 * @since 3.5.0
 	 *
@@ -718,7 +718,7 @@ class wpdb {
 	}
 
 	/**
-	 * Magic function, for backwards compatibility.
+	 * Magic function, for backward compatibility.
 	 *
 	 * @since 3.5.0
 	 *
diff --git a/wp-includes/wp-diff.php b/wp-includes/wp-diff.php
index 832a62f8b3..1248cd66b7 100644
--- a/wp-includes/wp-diff.php
+++ b/wp-includes/wp-diff.php
@@ -458,7 +458,7 @@ class WP_Text_Diff_Renderer_Table extends Text_Diff_Renderer {
 	}
 
 	/**
-	 * Make private properties readable for backwards compatibility.
+	 * Make private properties readable for backward compatibility.
 	 *
 	 * @since 4.0.0
 	 * @access public
@@ -473,7 +473,7 @@ class WP_Text_Diff_Renderer_Table extends Text_Diff_Renderer {
 	}
 
 	/**
-	 * Make private properties settable for backwards compatibility.
+	 * Make private properties settable for backward compatibility.
 	 *
 	 * @since 4.0.0
 	 * @access public
@@ -489,7 +489,7 @@ class WP_Text_Diff_Renderer_Table extends Text_Diff_Renderer {
 	}
 
 	/**
-	 * Make private properties checkable for backwards compatibility.
+	 * Make private properties checkable for backward compatibility.
 	 *
 	 * @since 4.0.0
 	 * @access public
@@ -504,7 +504,7 @@ class WP_Text_Diff_Renderer_Table extends Text_Diff_Renderer {
 	}
 
 	/**
-	 * Make private properties un-settable for backwards compatibility.
+	 * Make private properties un-settable for backward compatibility.
 	 *
 	 * @since 4.0.0
 	 * @access public