acknowledge
1 accede, accept, acquiesce, admit, allow, concede, confess, declare, grant, own, profess, recognize, yield
2 address, greet, hail, notice, recognize, salute
3 answer, notice, react to, recognize, reply to, respond to, return
Antonyms
1 contradict, deny, disclaim, discount, reject, renounce, repudiate
2 & 3 deny, disavow, disdain, disregard, ignore, rebut, reject, snub, spurn