Catholic religious orders are, historically, a category of Catholic religious institutes. Subcategories are canons regular (canons and canonesses regular who recite the divine office and serve a church and perhaps a parish); monastics; mendicants (friars or religious sisters who live from alms, recite the divine office, and, in the case of the men, participate in apostolic activities); and clerks regular (priests who take religious vows and have a very active apostolic life).