existing or occurring with something else, often in a lesser way; accompanying; concurrent

an event and its concomitant circumstances.

a concomitant quality, circumstance, or thing.

adjective

accidental , chance , unrelated

adjective

accessory , adjuvant , agreeing , ancillary , associated with , associative , attendant , attending , belonging , coefficient , coetaneous , coeval , coexistent , coincident , coincidental , collateral , complementary , concordant , concurrent , conjoined , conjoined with , connected , contemporaneous , contemporary , coordinate , corollary , coterminous , coupled with , fellow , incident , in tempo , in time , isochronal , isochronous , joint , satellite , synchronal , synchronous , synergetic , synergistic , accompanying , associate , companion , consort , contributing

noun

associate , attendant , companion