なければいけない / なければならない
- 1Must or have to do something because of a personal or situational need, such as a deadline.Ex. 1
- 2Must do something as a duty, rule, or general obligation, typically phrased with なければならない.Ex. 2
Verb (nai-form minus い)The nai-form with only the final い removed, leaving …な.
行かな・食べな・しな・来（こ）な
Usually followed by くて・ければ・かった, as in 行かなければ.
i-adj. stemWhat is left once the final い is removed (the stem).
高・おいし・新し
いい first becomes よい: よさそう・よすぎる.
na-adj. stemA na-adjective without な, i.e. the form listed in a dictionary.
静か・きれい・好き
Add な before a noun (静かな部屋); as a predicate, follow it with だ／です (静かだ).
Polite: いけない becomes いけません, ならない becomes なりません
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A core expression of obligation, used in both speech and writing. なければいけない is common in conversation and personal situations. なければならない is preferred in writing, formal speech, and statements about duties, laws, or general truths. It is essentially synonymous with なくてはいけない. Unlike べきだ, which gives advice about what one ought to do, it states necessity.
Do not attach なければ to the dictionary form; use the ない-form stem (出さなければ, not 出すなければ).
Note that nouns and な-adjectives require で before なければ (学生でなければならない, not 学生なければならない).
Learners sometimes use it to tell superiors what to do, which can sound like a command rather than advice.
- 1.なくてはいけない / なくてはならないN4「なくてはいけない / なくてはならない」is basically identical in meaning and usage and generally interchangeable with this pattern, including how いけない vs ならない split roles. The difference is purely formal: use 「なくては」, e.g., 「書かなくては」, which contracts to 「なくちゃ」in speech.
- 2.ねばならないN2「ねばならない」has essentially the same meaning but is a literary-sounding variant of 「なければならない」—stiff and solemn, used mainly in writing and speeches rather than daily conversation. Attach it as する→「せねば」and nouns+「であらねば」。
- 3.なくちゃN5「なくちゃ」is the colloquial contraction of 「なくてはいけない」and means 'must,' just like this pattern, often with the ending dropped. Use it when talking to yourself or close people; in formal situations or toward superiors say 「なければなりません」。
- 4.〜ないわけにはいかないN1「ないわけにはいかない」attaches only to verbs and usually refers to the speaker's own actions, conveying reluctance forced by social obligations, position, or circumstances. For legal-style objective duties, stick with 「なければならない」rather than swapping it in.
- 5.べきだN2「べきだ」reflects the speaker's subjective judgment about what should be done based on reason or common sense, while this pattern stresses objective necessity or duty. The same situation often allows either, depending on perspective; it takes the dictionary form, and 「べきだった」can express regret.
- 6.わけにはいかないN3「わけにはいかない」with the dictionary form means 'cannot do something' due to propriety or one's situation. With the negative form it becomes 'cannot help doing,' which is closer to this pattern—but it emphasizes moral constraint or responsibility and attaches only to verbs.
なくてはいけない / ならない is essentially synonymous, and なくちゃ is its casual spoken contraction; ねばならない is a literary, more formal equivalent, and べきだ expresses what one ought to do rather than strict necessity. ないわけにはいかない means one cannot avoid doing something because circumstances or social considerations make not doing it unacceptable, while わけにはいかない means circumstances or social considerations make doing something unacceptable or impractical, not that it is impossible.
