regular
adj//ˈrɛɡ.(j)ʊ.ləʳ//regelbunden, stamgäst, stamkund
Having a constant pattern; showing evenness of form or appearance. [from 15th c.]
Demonstrating a consistent set of rules; showing order, evenness of operation or occurrence. [from 16th c.]
Happening at constant (especially short) intervals. [from 17th c.]
(grammar, of a verb, plural, etc) Following a set or common pattern; according to the normal rules of a given language. [from 17th c.]
A frequent, routine visitor to an establishment.
A frequent customer, client or business partner.