category_exists( int|string $cat_name, int $parent = null )

Source

File: wp-admin/includes/taxonomy.php

function category_exists( $cat_name, $parent = null ) {
	$id = term_exists( $cat_name, 'category', $parent );
	if ( is_array( $id ) ) {
		$id = $id['term_id'];
	}
	return $id;
}