Obligation (Must / Have to)

5 related grammar points that express the same core idea - compared below so you can tell which one to reach for.

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なきゃ / なければならない

Writing, or speaking in a formal setting (a report, an announcement, talking to a superior).

vs : Use なければならない, the full uncontracted form. なきゃいけない and なくちゃいけない are casual spoken contractions that sound too informal in writing. ねばならない is a step more literary again, common in rules and textbooks.