하나를 보면 열을 안다

hanareul bomyeon yeoreul anda

Word for word

“See one thing and you know ten.”

What it means

One small action shows you what someone is like overall.

When you'd say it

Judging someone by how they treat waiters, or how they keep a small promise.

Example

첫 만남에 직원한테 반말하더라. 하나를 보면 열을 알지.He was rude to the waiter on our first date. See one, know ten.