diff --git a/assets/src/settings-page/paired-url-structure.js b/assets/src/settings-page/paired-url-structure.js
index f5ac04b0750..af8f3b98c79 100644
--- a/assets/src/settings-page/paired-url-structure.js
+++ b/assets/src/settings-page/paired-url-structure.js
@@ -18,7 +18,7 @@ import { AMPNotice, NOTICE_TYPE_INFO, NOTICE_SIZE_LARGE } from '../components/am
 
 /**
  * @typedef {{name: string, slug: string, type: string}} Source
- * @typedef {{query_param: string[], path_suffix: string[], legacy_transitional: string[], legacy_reader: string[], custom: string[]}} PairedUrlExamplesData
+ * @typedef {{query_var: string[], path_suffix: string[], legacy_transitional: string[], legacy_reader: string[], custom: string[]}} PairedUrlExamplesData
  */
 
 /**
@@ -152,16 +152,16 @@ export function PairedUrlStructure( { focusedSection } ) {
 			<ul>
 				<li>
 					<input
-						id="paired_url_structure_query_param"
+						id="paired_url_structure_query_var"
 						type="radio"
 						name="paired_url_structure"
-						checked={ 'query_param' === editedOptions.paired_url_structure }
+						checked={ 'query_var' === editedOptions.paired_url_structure }
 						onChange={ () => {
-							updateOptions( { paired_url_structure: 'query_param' } );
+							updateOptions( { paired_url_structure: 'query_var' } );
 						} }
 						disabled={ isCustom }
 					/>
-					<label htmlFor="paired_url_structure_query_param">
+					<label htmlFor="paired_url_structure_query_var">
 						{ __( 'Query parameter', 'amp' ) + ': ' }
 						<code>
 							{ `?${ slug }=1` }
@@ -171,7 +171,7 @@ export function PairedUrlStructure( { focusedSection } ) {
 							{ __( '(recommended)', 'amp' ) }
 						</em>
 					</label>
-					<PairedUrlExamples pairedUrls={ editedOptions.paired_url_examples.query_param } />
+					<PairedUrlExamples pairedUrls={ editedOptions.paired_url_examples.query_var } />
 				</li>
 				<li>
 					<input
diff --git a/includes/options/class-amp-options-manager.php b/includes/options/class-amp-options-manager.php
index c0b02d0fedb..fc52242b234 100644
--- a/includes/options/class-amp-options-manager.php
+++ b/includes/options/class-amp-options-manager.php
@@ -35,7 +35,7 @@ class AMP_Options_Manager {
 		Option::SUPPORTED_TEMPLATES     => [ 'is_singular' ],
 		Option::VERSION                 => AMP__VERSION,
 		Option::READER_THEME            => ReaderThemes::DEFAULT_READER_THEME,
-		Option::PAIRED_URL_STRUCTURE    => Option::PAIRED_URL_STRUCTURE_QUERY_PARAM,
+		Option::PAIRED_URL_STRUCTURE    => Option::PAIRED_URL_STRUCTURE_QUERY_VAR,
 		Option::PLUGIN_CONFIGURED       => false,
 	];
 
diff --git a/src/Option.php b/src/Option.php
index f5d18224f26..9df7ae348c3 100644
--- a/src/Option.php
+++ b/src/Option.php
@@ -46,20 +46,20 @@ interface Option {
 	/**
 	 * Indicate the structure for paired AMP URLs.
 	 *
-	 * Default value: 'query_param'
+	 * Default value: 'query_var'
 	 *
 	 * @var string
 	 */
 	const PAIRED_URL_STRUCTURE = 'paired_url_structure';
 
 	/**
-	 * Query param paired URL structure.
+	 * Query var paired URL structure.
 	 *
 	 * This is the default, where all AMP URLs end in `?amp=1`.
 	 *
 	 * @var string
 	 */
-	const PAIRED_URL_STRUCTURE_QUERY_PARAM = 'query_param';
+	const PAIRED_URL_STRUCTURE_QUERY_VAR = 'query_var';
 
 	/**
 	 * Path suffix paired URL structure.
diff --git a/src/PairedRouting.php b/src/PairedRouting.php
index a5433ef35d4..20c52720720 100644
--- a/src/PairedRouting.php
+++ b/src/PairedRouting.php
@@ -17,7 +17,7 @@
 use AmpProject\AmpWP\Admin\ReaderThemes;
 use AmpProject\AmpWP\PairedUrlStructure\LegacyReaderUrlStructure;
 use AmpProject\AmpWP\PairedUrlStructure\LegacyTransitionalUrlStructure;
-use AmpProject\AmpWP\PairedUrlStructure\QueryParamUrlStructure;
+use AmpProject\AmpWP\PairedUrlStructure\QueryVarUrlStructure;
 use AmpProject\AmpWP\PairedUrlStructure\PathSuffixUrlStructure;
 use WP_Query;
 use WP_Rewrite;
@@ -42,7 +42,7 @@ final class PairedRouting implements Service, Registerable {
 	 * @var string[]
 	 */
 	const PAIRED_URL_STRUCTURES = [
-		Option::PAIRED_URL_STRUCTURE_QUERY_PARAM         => QueryParamUrlStructure::class,
+		Option::PAIRED_URL_STRUCTURE_QUERY_VAR           => QueryVarUrlStructure::class,
 		Option::PAIRED_URL_STRUCTURE_PATH_SUFFIX         => PathSuffixUrlStructure::class,
 		Option::PAIRED_URL_STRUCTURE_LEGACY_TRANSITIONAL => LegacyTransitionalUrlStructure::class,
 		Option::PAIRED_URL_STRUCTURE_LEGACY_READER       => LegacyReaderUrlStructure::class,
@@ -197,7 +197,7 @@ public function get_paired_url_structure() {
 				if ( array_key_exists( $structure_slug, self::PAIRED_URL_STRUCTURES ) ) {
 					$structure_class = self::PAIRED_URL_STRUCTURES[ $structure_slug ];
 				} else {
-					$structure_class = QueryParamUrlStructure::class;
+					$structure_class = QueryVarUrlStructure::class;
 				}
 			}
 
@@ -255,7 +255,7 @@ public function filter_rest_options( $options ) {
 			$options[ Option::PAIRED_URL_STRUCTURE ] = AMP_Options_Manager::get_option( Option::PAIRED_URL_STRUCTURE );
 
 			// Handle edge case where an unrecognized paired URL structure was saved.
-			if ( ! in_array( $options[ Option::PAIRED_URL_STRUCTURE ], self::PAIRED_URL_STRUCTURES, true ) ) {
+			if ( ! in_array( $options[ Option::PAIRED_URL_STRUCTURE ], array_keys( self::PAIRED_URL_STRUCTURES ), true ) ) {
 				$defaults = $this->filter_default_options( [], $options );
 
 				$options[ Option::PAIRED_URL_STRUCTURE ] = $defaults[ Option::PAIRED_URL_STRUCTURE ];
@@ -558,7 +558,7 @@ public function is_using_permalinks() {
 	 * @return array Defaults.
 	 */
 	public function filter_default_options( $defaults, $options ) {
-		$value = Option::PAIRED_URL_STRUCTURE_QUERY_PARAM;
+		$value = Option::PAIRED_URL_STRUCTURE_QUERY_VAR;
 
 		if (
 			isset( $options[ Option::VERSION ], $options[ Option::THEME_SUPPORT ], $options[ Option::READER_THEME ] )
diff --git a/src/PairedUrlStructure/QueryParamUrlStructure.php b/src/PairedUrlStructure/QueryVarUrlStructure.php
similarity index 78%
rename from src/PairedUrlStructure/QueryParamUrlStructure.php
rename to src/PairedUrlStructure/QueryVarUrlStructure.php
index ce1ba598fea..8e94de2eb3f 100644
--- a/src/PairedUrlStructure/QueryParamUrlStructure.php
+++ b/src/PairedUrlStructure/QueryVarUrlStructure.php
@@ -12,11 +12,14 @@
 /**
  * Descriptor for paired URL structures that include the `?amp=1` query parameter.
  *
+ * A query parameter is also known as a query arg and a query var. Given prior usage of "query var" in the codebase,
+ * the slug for the paired URL structure is `query_var` whereas in the UI it is presented as "query parameter".
+ *
  * @package AmpProject\AmpWP
  * @since 2.1
  * @internal
  */
-final class QueryParamUrlStructure extends PairedUrlStructure {
+final class QueryVarUrlStructure extends PairedUrlStructure {
 
 	/**
 	 * Turn a given URL into a paired AMP URL.
diff --git a/tests/php/src/PairedRoutingTest.php b/tests/php/src/PairedRoutingTest.php
index ab6d28f6d1d..8abdf79742f 100644
--- a/tests/php/src/PairedRoutingTest.php
+++ b/tests/php/src/PairedRoutingTest.php
@@ -11,7 +11,7 @@
 use AmpProject\AmpWP\PairedUrlStructure\LegacyReaderUrlStructure;
 use AmpProject\AmpWP\PairedUrlStructure\LegacyTransitionalUrlStructure;
 use AmpProject\AmpWP\PairedUrlStructure\PathSuffixUrlStructure;
-use AmpProject\AmpWP\PairedUrlStructure\QueryParamUrlStructure;
+use AmpProject\AmpWP\PairedUrlStructure\QueryVarUrlStructure;
 use AmpProject\AmpWP\Tests\Helpers\AssertContainsCompatibility;
 use AMP_Options_Manager;
 use AMP_Theme_Support;
@@ -67,9 +67,9 @@ public function test_register() {
 	/** @return array */
 	public function get_data_for_test_get_paired_url_structure() {
 		return [
-			'query_param'         => [
-				Option::PAIRED_URL_STRUCTURE_QUERY_PARAM,
-				QueryParamUrlStructure::class,
+			'query_var'           => [
+				Option::PAIRED_URL_STRUCTURE_QUERY_VAR,
+				QueryVarUrlStructure::class,
 			],
 			'path_suffix'         => [
 				Option::PAIRED_URL_STRUCTURE_PATH_SUFFIX,
@@ -85,7 +85,7 @@ public function get_data_for_test_get_paired_url_structure() {
 			],
 			'bogus'               => [
 				'bogus',
-				QueryParamUrlStructure::class,
+				QueryVarUrlStructure::class,
 			],
 		];
 	}
@@ -202,15 +202,15 @@ public function test_get_endpoint_path_slug_conflicts() {
 	/** @return array */
 	public function get_data_for_test_paired_requests() {
 		return [
-			'query_param_reader_mode_amp'           => [
+			'query_var_reader_mode_amp'             => [
 				AMP_Theme_Support::READER_MODE_SLUG,
-				Option::PAIRED_URL_STRUCTURE_QUERY_PARAM,
+				Option::PAIRED_URL_STRUCTURE_QUERY_VAR,
 				'/?amp=1',
 				true,
 			],
-			'query_param_reader_mode_non_amp'       => [
+			'query_var_reader_mode_non_amp'         => [
 				AMP_Theme_Support::READER_MODE_SLUG,
-				Option::PAIRED_URL_STRUCTURE_QUERY_PARAM,
+				Option::PAIRED_URL_STRUCTURE_QUERY_VAR,
 				'/',
 				false,
 			],
@@ -240,7 +240,7 @@ public function get_data_for_test_paired_requests() {
 			],
 			'standard_mode'                         => [
 				AMP_Theme_Support::STANDARD_MODE_SLUG,
-				Option::PAIRED_URL_STRUCTURE_QUERY_PARAM,
+				Option::PAIRED_URL_STRUCTURE_QUERY_VAR,
 				'/',
 				null,
 			],
@@ -311,8 +311,8 @@ function ( $query_vars ) use ( &$request_uri_during_parse_request ) {
 	/** @return array */
 	public function get_data_for_test_initialize_paired_request() {
 		return [
-			'query_param' => [
-				Option::PAIRED_URL_STRUCTURE_QUERY_PARAM,
+			'query_var'   => [
+				Option::PAIRED_URL_STRUCTURE_QUERY_VAR,
 				false,
 			],
 			'path_suffix' => [
@@ -351,7 +351,7 @@ public function test_initialize_paired_request( $structure, $filtering_unique_po
 	/** @covers ::initialize_paired_request() */
 	public function test_initialize_paired_request_in_standard_mode() {
 		AMP_Options_Manager::update_option( Option::THEME_SUPPORT, AMP_Theme_Support::STANDARD_MODE_SLUG );
-		AMP_Options_Manager::update_option( Option::PAIRED_URL_STRUCTURE, Option::PAIRED_URL_STRUCTURE_QUERY_PARAM );
+		AMP_Options_Manager::update_option( Option::PAIRED_URL_STRUCTURE, Option::PAIRED_URL_STRUCTURE_QUERY_VAR );
 		$this->instance->initialize_paired_request();
 		$this->assertNull( $this->get_private_property( $this->instance, 'did_request_endpoint' ) );
 		$this->assertFalse( has_filter( 'do_parse_request', [ $this->instance, 'extract_endpoint_from_environment_before_parse_request' ] ) );
@@ -468,7 +468,7 @@ public function get_data_for_test_filter_default_options() {
 					Option::THEME_SUPPORT => AMP_Theme_Support::TRANSITIONAL_MODE_SLUG,
 					Option::READER_THEME  => ReaderThemes::DEFAULT_READER_THEME,
 				],
-				Option::PAIRED_URL_STRUCTURE_QUERY_PARAM,
+				Option::PAIRED_URL_STRUCTURE_QUERY_VAR,
 			],
 			'old_version_transitional'  => [
 				[
@@ -819,10 +819,10 @@ static function ( $url ) use ( &$redirected_url ) {
 	public function test_redirect_extraneous_paired_endpoint_canonical_extraneous_query_var() {
 		AMP_Options_Manager::update_option( Option::THEME_SUPPORT, AMP_Theme_Support::STANDARD_MODE_SLUG );
 		$this->set_permalink_structure( '/%year%/%monthnum%/%day%/%postname%/' );
-		$query_param_structure = $this->injector->make( QueryParamUrlStructure::class );
+		$query_var_structure = $this->injector->make( QueryVarUrlStructure::class );
 
 		$permalink_url    = get_permalink( self::factory()->post->create() );
-		$amp_endpoint_url = $query_param_structure->add_endpoint( $permalink_url );
+		$amp_endpoint_url = $query_var_structure->add_endpoint( $permalink_url );
 		$this->go_to( $amp_endpoint_url );
 
 		$this->assertTrue( amp_is_canonical() );
@@ -843,7 +843,7 @@ static function ( $url ) use ( &$redirected_url ) {
 	/** @covers ::redirect_extraneous_paired_endpoint() */
 	public function test_redirect_extraneous_paired_endpoint_path_suffix_404() {
 		AMP_Options_Manager::update_option( Option::THEME_SUPPORT, AMP_Theme_Support::TRANSITIONAL_MODE_SLUG );
-		AMP_Options_Manager::update_option( Option::PAIRED_URL_STRUCTURE, Option::PAIRED_URL_STRUCTURE_QUERY_PARAM );
+		AMP_Options_Manager::update_option( Option::PAIRED_URL_STRUCTURE, Option::PAIRED_URL_STRUCTURE_QUERY_VAR );
 		$this->set_permalink_structure( '/%year%/%monthnum%/%day%/%postname%/' );
 		$path_suffix_structure = $this->injector->make( PathSuffixUrlStructure::class );
 		$paired_url            = $this->injector->make( PairedUrl::class );
@@ -873,7 +873,7 @@ static function ( $url ) use ( &$redirected_url ) {
 	/** @covers ::redirect_extraneous_paired_endpoint() */
 	public function test_redirect_extraneous_paired_endpoint_slug_redirect() {
 		AMP_Options_Manager::update_option( Option::THEME_SUPPORT, AMP_Theme_Support::TRANSITIONAL_MODE_SLUG );
-		AMP_Options_Manager::update_option( Option::PAIRED_URL_STRUCTURE, Option::PAIRED_URL_STRUCTURE_QUERY_PARAM );
+		AMP_Options_Manager::update_option( Option::PAIRED_URL_STRUCTURE, Option::PAIRED_URL_STRUCTURE_QUERY_VAR );
 		AMP_Options_Manager::update_option( Option::ALL_TEMPLATES_SUPPORTED, false );
 		AMP_Options_Manager::update_option( Option::SUPPORTED_TEMPLATES, [ 'is_singular' ] );
 		$this->set_permalink_structure( '/%year%/%monthnum%/%day%/%postname%/' );
@@ -918,7 +918,7 @@ static function ( $url ) {
 	/** @covers ::redirect_extraneous_paired_endpoint() */
 	public function test_redirect_extraneous_paired_endpoint_unavailable_template() {
 		AMP_Options_Manager::update_option( Option::THEME_SUPPORT, AMP_Theme_Support::TRANSITIONAL_MODE_SLUG );
-		AMP_Options_Manager::update_option( Option::PAIRED_URL_STRUCTURE, Option::PAIRED_URL_STRUCTURE_QUERY_PARAM );
+		AMP_Options_Manager::update_option( Option::PAIRED_URL_STRUCTURE, Option::PAIRED_URL_STRUCTURE_QUERY_VAR );
 		AMP_Options_Manager::update_option( Option::ALL_TEMPLATES_SUPPORTED, false );
 		AMP_Options_Manager::update_option( Option::SUPPORTED_TEMPLATES, [ 'is_singular' ] );
 		$this->set_permalink_structure( '/%year%/%monthnum%/%day%/%postname%/' );
diff --git a/tests/php/src/PairedUrlStructure/QueryVarUrlStructureTest.php b/tests/php/src/PairedUrlStructure/QueryVarUrlStructureTest.php
index 65964f4d639..38c908cec39 100644
--- a/tests/php/src/PairedUrlStructure/QueryVarUrlStructureTest.php
+++ b/tests/php/src/PairedUrlStructure/QueryVarUrlStructureTest.php
@@ -2,18 +2,18 @@
 
 namespace AmpProject\AmpWP\Tests\PairedUrlStructure;
 
-use AmpProject\AmpWP\PairedUrlStructure\QueryParamUrlStructure;
+use AmpProject\AmpWP\PairedUrlStructure\QueryVarUrlStructure;
 use AmpProject\AmpWP\Tests\DependencyInjectedTestCase;
 
-/** @coversDefaultClass \AmpProject\AmpWP\PairedUrlStructure\QueryParamUrlStructure */
+/** @coversDefaultClass \AmpProject\AmpWP\PairedUrlStructure\QueryVarUrlStructure */
 class QueryVarUrlStructureTest extends DependencyInjectedTestCase {
 
-	/** @var QueryParamUrlStructure */
+	/** @var QueryVarUrlStructure */
 	private $instance;
 
 	public function setUp() {
 		parent::setUp();
-		$this->instance = $this->injector->make( QueryParamUrlStructure::class );
+		$this->instance = $this->injector->make( QueryVarUrlStructure::class );
 	}
 
 	/** @covers ::add_endpoint() */
diff --git a/tests/php/test-amp-helper-functions.php b/tests/php/test-amp-helper-functions.php
index 970f4315704..f41d0be43ab 100644
--- a/tests/php/test-amp-helper-functions.php
+++ b/tests/php/test-amp-helper-functions.php
@@ -1849,7 +1849,7 @@ public function test_amp_add_paired_endpoint() {
 	public function data_amp_has_paired_endpoint() {
 		return [
 			'nothing'                 => [
-				Option::PAIRED_URL_STRUCTURE_QUERY_PARAM,
+				Option::PAIRED_URL_STRUCTURE_QUERY_VAR,
 				'',
 				false,
 			],
@@ -1859,7 +1859,7 @@ public function data_amp_has_paired_endpoint() {
 				true,
 			],
 			'url_param_value'         => [
-				Option::PAIRED_URL_STRUCTURE_QUERY_PARAM,
+				Option::PAIRED_URL_STRUCTURE_QUERY_VAR,
 				'?amp=1',
 				true,
 			],
diff --git a/tests/php/test-class-amp-options-manager.php b/tests/php/test-class-amp-options-manager.php
index 233fcb38ac7..ae8a4610ce4 100644
--- a/tests/php/test-class-amp-options-manager.php
+++ b/tests/php/test-class-amp-options-manager.php
@@ -160,7 +160,7 @@ public function test_get_and_set_options() {
 				Option::MOBILE_REDIRECT         => false,
 				Option::READER_THEME            => 'legacy',
 				Option::PLUGIN_CONFIGURED       => false,
-				Option::PAIRED_URL_STRUCTURE    => Option::PAIRED_URL_STRUCTURE_QUERY_PARAM,
+				Option::PAIRED_URL_STRUCTURE    => Option::PAIRED_URL_STRUCTURE_QUERY_VAR,
 			],
 			AMP_Options_Manager::get_options()
 		);