A statement made when one party concurs with another, thus putting them into agreement.
“Whenever people agree with me I always feel I must be wrong.”
-- Oscar Wilde
My response phrase whenever a coworker notices me noticing them yawning. The habit started as way to break the tension in case they felt embarassed and also to let them know that I understand and commiserate with the implied fatigue. Now, however, I say it when I see someone yawn, possibly initiating what I had intended to alleviate. Awkward.
See also: Yep; Indeed; Amen; You right, you right; 10-4; Assent; Uff da; Yeet; Oh, hell yes; Word; Okay; Sure.