1.declare to be true or admit the existence or reality or truth of;
He admitted his errors
2.report the receipt of;
The program committee acknowledged the submission of the authors of the paper
3.express recognition of the presence or existence of, or acquaintance with;
He never acknowledges his colleagues when they run into him in the hallway
4.express obligation, thanks, or gratitude for;
We must acknowledge the kindness she showed towards us
5.accept as legally binding and valid;
acknowledge the deed
6.accept (someone) to be what is claimed or accept his power and authority;
The Crown Prince was acknowledged as the true heir to the throne