U

acknowledge

verb (used with object), ac·knowl·edged, ac·knowl·edg·ing.

to admit to be real or true; recognize the existence, truth, or fact of: to acknowledge one’s mistakes.
to show or express recognition or realization of: to acknowledge an acquaintance by nodding.
to recognize the authority, validity, or claims of: The students acknowledged the authority of the student council.
to show or express appreciation or gratitude for: to acknowledge a favor.
to indicate or make known the receipt of: to acknowledge a letter.
to take notice of or reply to: to acknowledge a greeting.
Law. to confirm as binding or of legal force: to acknowledge a deed.

verb (tr)

(may take a clause as object) to recognize or admit the existence, truth, or reality of
to indicate recognition or awareness of, as by a greeting, glance, etc
to express appreciation or thanks forto acknowledge a gift
to make the receipt of known to the senderto acknowledge a letter
to recognize, esp in legal form, the authority, rights, or claims of

1550s, a blend of Middle English aknow (from Old English oncnawan “understand,” from on + cnawan “recognize;” see know) and Middle English knowlechen “admit, acknowledge” (c.1200; see knowledge). In the merger, a parasitic -c- slipped in, so that while the kn- became a simple “n” sound (as in know), the -c- stepped up to preserve, in this word, the ancient “kn-” sound. Related: Acknowledged; acknowledging.