All 4 Uses of

acknowledge
in
Change of Heart, by Picoult

No one went out of their way to acknowledge him, much less offer him something as precious as a piece of gum.†
*

acknowledge = recognize

I walked inside, acknowledged the CO, and sat down on the edge of Shay's bed.†

acknowledged = recognized

So even if Shay didn't acknowledge me in court, I would still be there.†

acknowledge = recognize

It's far easier to tell yourself your daughter is still a little girl than to see her in a bikini and realize she has the curves of a young woman; it's safer to say you are a good parent who has all the right conversations about drugs and sex than to acknowledge there are a thousand things she would never tell you.†

Definitions:

(1) (acknowledge as in: acknowledge her or the truth)
express recognition or appreciation of someone or something; or admit something
(2) (meaning too rare to warrant focus)
meaning too rare to warrant focus:

Specialized senses include sending an "acknowledgement" (letter or other message) to indicate that something was received and the "acknowledgements" section at the beginning of a book where an author recognizes and thanks other people who helped in creating the book or ideas contained in it.