1. To admit the existence or truth of: The doctors acknowledged that the treatment had not been successful.
2.
a. To express recognition of; make notice of: "When he saw me acknowledge him, he smiled as if we were dear friends" (Angela Patrinos).
b. To express gratitude or appreciation for or to: acknowledged the contributions of the volunteers; acknowledged her editor in the preface to the book.
3. To report the receipt of (something) to the sender or giver: acknowledge a letter.
4. Law To accept or certify as legally binding: acknowledge a deed of ownership.