To cheer on somebody or give a helping comment.

When you both recognize that you've 1)been wrong about something or 2)have hurt/insulted someone AND want to apologize for said transgression with the convenience of a single world

To accept, admit, or recognize something, or the truth or existence of something.

to accept that something is true
acknowledge something She refuses to acknowledge the need for reform.
Are you prepared to acknowledge your responsibility?
acknowledge that… The government acknowledged that the tax was unfair.
acknowledge something to be, have, etc. something It is generally acknowledged to be true.

Something senpai will never do.

Someone who without fail will acknowledge those around them in passing. Usually in an office environment. Generally it is perceived as polite at first, but will soon grow tiresome.

the act of acknowledging