http://dictionary.cambridge.org/dictionary/british/acknowledge
acknowledge: to accept, admit, or recognize something, or the truth or existence of something.
[+ -ing verb] She acknowledged having been at fault.
[+ that] She acknowledged that she had been at fault.
You must acknowledge the truth of her argument.
Historians generally acknowledge her as a genius in her field.
[+ obj + to infinitive ] She is usually acknowledged to be one of our best artists.
They refused to acknowledge (= to recognize officially) the new government.
He didn't even acknowledge my presence (= show that he had seen me).
The government won't even acknowledge the existence of the problem.