Having good intelligence or judgment; clever and able to act appropriately in situations.
彼は問題をすぐに理解する賢い学生だ。
He is a smart student who understands problems quickly.
賢い判断を下すことが重要だ。
It's important to make a wise decision.
あの犬はとても賢くて、芸をすぐ覚えた。
That dog is very clever and learned tricks quickly.
Used especially for children or pets to mean well-behaved, obedient, or easy to manage (a colloquial/regional usage).
うちの子は今日は賢くしているよ。
My child has been well-behaved today.
犬が賢くて、呼べばすぐに来る。
The dog is obedient and comes when called.