This grammar means you must do something. It shows that an action is very important to do.
Verb [なくて-form] + は + いけないPrimary
Verb [なくちゃ-form] + いけない
This grammar means you must do something. It shows that an action is very important to do.
ビザを更新するために、大使館に行かなくてはいけない。
I have to go to the embassy to renew my visa.
子供が熱を出したので、昨日は会社を休まなくてはいけなかった。
My child had a fever, so I had to take the day off from work yesterday.
試験のために勉強しなくてはいけないので、遊びには行けません。
Because I have to study for the exam, I can't go out to have fun.
試合に勝つためには、もっと練習しなくてはいけない。
In order to win the match, we have to practice more.
ごめん、もう行かなくちゃいけないんだ。
Sorry, I have to go now.
The word "は" makes the "must do" feeling stronger. It is like putting a spotlight on the need to do something. In daily talk, "は" often changes to "ちゃ". This makes "〜なくちゃいけない" a common way to speak. The full form "〜なくてはいけない" sounds more formal. You can use it when writing or in polite speech.
This is like saying "must do." It is not as formal as "-nakereba naranai." It is also not as casual as "-nai to ikenai." It is a normal way to say something is necessary.
Watch out: Do not mix up "-nakute wa ikenai" and "-te wa ikenai". "-nakute wa ikenai" means you must do something. It uses a verb that means "not doing". This means "not doing is not good". "-te wa ikenai" means you must not do something. It uses a verb that means "doing". For example, "kusuri o nomanakute wa ikenai" means "I must take medicine". "Kono kusuri o nonde wa ikenai" means "You must not take this medicine".
Often confused with(1)
Track your mastery
Kumi's KMT system tracks your mastery across kanji, vocabulary, grammar, and reading. Create a free account to use it on 220,000+ concepts.