Grammar Info

N5 Lesson 9: 7/13

～てはいけないMust not, May not

Structure

Verb［て］+ は + いけない

Details

  • Part of Speech

    Verb

  • Word Type

    Auxiliary Verb

  • Register

    Formal

About てはいけない

てはいけない is used in Japanese to express that (A) 'cannot', or 'must not' be done. It is the combination of a verb in て form, the は particle, and the negative potential form of 行(い)く (to be able to go). In this way, it literally means '(A) cannot/is not able to go'.

Although は can be dropped from many phrases and expressions, the は in this particular grammar point is usually not. This is because いけない would then become the second action in a sequence of events (the usual function of て form). However, to make this more casual, ては is often changed to ちゃ (ては becomes ちゃ), or じゃ (では becomes じゃ), as this is easier to say.

Caution

Apart from いけない; ならない and だめ are also frequently used to get across the same meaning. However, they are used in different situations.

いけない - Fairly neutral. Used in both spoken and written language.

ならない - Fairly formal. Used mostly in written language.

だめ - Very casual. Used almost exclusively in spoken language.

Examples

--:--

    そこに入(はい)ってはいけない。

    You must not go in there.

    クジラを食(た)べてはいけない。

    We must not eat whale.

    このビルに入(はい)ってはいけない。

    You must not go into this building.

    晩(ばん)ごはんの前(まえ)に、お菓子(かし)を食(た)べてはいけない。

    You must not eat candy before dinner.

    この池(いけ)で泳(およ)いではいけません。

    You must not swim in this pond.

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てはいけない – Grammar Discussion

Most Recent Replies (19 in total)

  • ResFort

    ResFort

    This construction uses the potential form of 行く (行ける, “can go”), not the dictionary form.
    So when conjugating it into the negative we get いけない/いけません (行ける itself is an ichidan verb).

    The literal translation for Aてはいけない is then something like “doing A cannot go”, which is better interpreted as “must not do A”.

  • GrimeyPlopFlop

    GrimeyPlopFlop

    Ah, that makes a a lot of sense, thank you!

  • notasas

    notasas

    The bunpro description states this contains “negative potential form of 行く”, however I’ve just encountered this:

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