What it means
なくちゃ expresses that someone must do something or needs to do something. It is a shortened, familiar form of なくては, used after the negative stem of a verb. It is common in everyday speech and often appears at the end of a sentence. The obligation is usually understood from context, and the subject may be omitted.
Usage note
なくちゃ is familiar and somewhat casual. In polite situations, use the full polite counterpart なくてはいけません instead. Do not confuse it with なくちゃいけない, which also expresses obligation but includes いけない explicitly.
How to use it
Verb negative stemなくてはいけません
私は行かなくてはいけません。
I must go.
Verb negative stemなくちゃ
私は行かなくちゃ。
I must go.
Example sentences
明日の朝、病院へ行かなくちゃ。
I have to go to the hospital tomorrow morning.
図書館の本を返さなくちゃ。
I have to return the library book.
寝る前に歯を磨かなくちゃ。
I have to brush my teeth before going to bed.
駅で切符を買