Acknowledgement and Affirmation are two words that are often used interchangeably, yet they have distinct meanings.
Acknowledgement is the recognition and acceptance of something that one has done, said, or believed. It is the recognition of another's accomplishments, skills, and contributions and can also be used to show appreciation or sympathy. For example, a teacher sending a note to a student's parents to acknowledge their child's excellent performance on a test.
Affirmation on the other hand, is an act of declaring that something is true. It is an act of expressing approval, or a statement of positive affirmation. For example, a teacher giving an affirmation to a student for their effort and progress.
In conclusion, Acknowledgement is the recognition and acceptance of something, while Affirmation is an act of declaring something is true.
References
https://www.merriam-webster.com/dictionary/acknowledgement
https://www.merriam-webster.com/dictionary/affirmation