Explanation
Expresses the necessity or obligation; 'must', 'have to'.
Formation
Verb-negative form + なくてはいけない
Detailed explanation
The ～なくてはいけない grammar point is used to express the necessity or obligation to do something. It can be translated as 'must' or 'have to' in English. The formation requires the negative form of a verb and is followed by いけない (cannot go/progress). It indicates that if something is not done, it will be a problem or inappropriate.
Examples
Shukudai o shinakute wa ikenai.
I have to do my homework.
Kono tegami o ashita made ni dasanakute wa ikenai.
I must send this letter by tomorrow.
Tabemono o muda ni shinakute wa ikenai.
We must not waste food.
Soutai shitai ga, jugyou ga owaru made matanakute wa ikenai.
I want to leave early, but I have to wait until the class finishes.
Practice
Grammar content sourced from hanabira.org.