tags

$tax_query = array(
	'relation' => 'OR',
	array(
		'taxonomy'         => 'post_tags',
		'terms'            => 'abc123',
		'field'            => 'slug',
		'operator'         => 'IN',
	),
	array(
		'taxonomy'         => 'post_tags',
		'terms'            => 'abc123',
		'field'            => 'slug',
		'operator'         => 'AND',
	),
);