(a.) Happening at the same instant.

accessory accidental accordant ado afloat afoot agreeing associate associated at one with attendant attending circumstantial coacting coactive coadunate coetaneous coeternal coeval coexistent coexisting coincident coinstantaneous collaborative collateral collective collusive combined combining concerted concomitant concordant concurrent concurring conjoint consilient conspiratorial contemporaneous contemporary conterminous cooperant cooperative coordinate correlative coterminous coupled coworking current doing eventuating fellow going on happening harmonious in hand in the wind incidental isochronal isochronous joined joint meeting mutual occasional occurring on on foot ongoing paired parallel parasitic passing prevailing prevalent resultant saprophytic simultaneous symbiotic synchronous synergetic synergic synergistic taking place twin under way unison unisonous united uniting