"Pat on the head" is a phrase used in American Engpsh to describe a gentle, affectionate touch or tap on someone's head, typically as a sign of fondness or praise. The origin of this phrase is unclear, but it is often used in casual or informal settings between friends, family members, or pets.

Example sentences:

"She gave her dog a pat on the head as a reward for good behavior."
"The father gave his son a pat on the head after he got a good grade on his test."

Translations:

她给了她的狗一个拍拍头，以奖励他的良好行为。
父亲在儿子考试得好成绩后，给了他一个摸摸头。