1The period from evening to late night; night. Can also be used adverbially (e.g. 'at night').
夜は静かになるので、勉強に集中できます。
It becomes quiet at night, so I can concentrate on studying.
彼は夜遅くまで働いて、朝に帰ってくる。
He works late into the night and comes home in the morning.
夜、窓の外を見たら星がきれいだった。
When I looked out the window at night, the stars were beautiful.
2Dinner; the evening meal (colloquial usage in some contexts or dialects).
母はもう夜を作り始めている。
My mother has already started making dinner.
今日の夜は何にする?
What shall we have for dinner today?
夜がまだできていないので、先にお風呂に入って。
Dinner isn't ready yet, so go take a bath first.