〜なければいけない

About

〜なければいけない combines a negative ば (conditional) form verb, with いけない ("can't go"). Together, they form a double negative (lit. "If not X, can't go") that describes things that "must" or "have to" be done.

〜なければいけない is a fairly formal way to say "must/have to", but is still often used in spoken Japanese. Its counterpart, 〜なければならない, is used more often in written Japanese.

〜なければいけない and other "must/have to" grammar that ends with いけない, tend to be used more for personal matters, rather than rules that apply to many people.

As always, 〜なければいけない can be made more polite by conjugating into the ます form (〜なければいけません).

Summary

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  〜なければいけない is a formal way to say "must/have to".

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  〜なければいけない tends to be used more for personal matters rather than rules that apply to many people.

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  〜なければいけない can be made more polite by conjugating into 〜なければいけません.