Filter WordPress login form labels

login-form-labels.php

<?php
/**
 * Filter login form labels
 *
 * @link https://wpartisan.me/?p=444
 * 
 */
add_action( 'login_head', 'ac_login_head_form_labels' );

function ac_login_head_form_labels() {

	add_filter( 'gettext', 'ac_login_form_labels', 20, 3 );

	function ac_login_form_labels( $translated_text, $text, $domain ) {
	
		if ( 'Username or Email Address' === $text ) {
			$translated_text = 'Email Address';
		}
	
		return $translated_text;
	
	}

}