/ækˈnɑlɪdʒ/
1.v.declare to be true or admit the existence or reality or truth of
“He admitted his errors”
2.v.report the receipt of
“The program committee acknowledged the submission of the authors of the paper”
3.v.express recognition of the presence or existence of, or acquaintance with
“He never acknowledges his colleagues when they run into him in the hallway”