Half: one of two equal parts of a whole; used for quantities, proportions, time, or degree. Can also function adverbially.
ケーキを半分に切ってください。
Please cut the cake in half.
彼は宿題を半分しか終えていない。
He has only finished half of his homework.
会議は半分の時間で終わった。
The meeting ended in half the time.
半分だけ味見してみた。
I tasted only half of it.