〜ないとは限らない

Might

Level 4Sounds Like naitohakagiranai

It is not necessarily the case that [X] won't happen. (It might happen).

How It Works

The pattern 〜ないとは限らない（ないとはかぎらない） is a double negative that translates to "it's not necessarily the case that [X] won't happen." This is a form of Partial Negation (部分否定), where you are acknowledging that while something is unlikely, the possibility still exists.

1. Nuance and Usage:
Unlike the neutral 〜かもしれない (might), this pattern is used to point out a potential risk or an exception to a general rule. It is often paired with the adverb 必ずしも（かならずしも） to emphasize that a situation is not 100% certain. It carries a nuance of caution, suggesting that one shouldn't be overconfident just because something seems safe.

2. Formation:
It attaches to the negative form of verbs, adjectives, and nouns:

  • Verbs: 〜ない form + とは限らない (e.g., 失敗しないとは限らない - It's not impossible that we'll fail).
  • I-Adjectives: 〜くない + とは限らない (e.g., 美味しくないとは限らない - It's not necessarily the case that it won't be delicious). Note: Often, using the opposite adjective with 〜とは限らない (e.g., 高いとは限らない) is more natural.
  • Na-Adjectives/Nouns: 〜ではない / 〜じゃない + とは限らない (e.g., 安全ではないとは限らない - It's not necessarily not safe).

3. Register:
This is a standard to formal expression common in written reports and professional settings. The variation 〜ないとも限らない is actually more emphatic or literary than the standard version. In casual daily conversation, speakers are more likely to use 〜かもしれない or 〜ないこともない to express similar ideas.

Examples (4)

  1. 十分準備をしても、失敗しないとは限らない。

    Even if you prepare thoroughly, it’s not necessarily the case that you won’t fail.

    Word by Word: Thorough preparation even if do, fail not that not limited.

    This uses the verb 失敗する（しっぱいする - to fail） in its negative form to warn that success is never 100% guaranteed.

  2. 今は健康でも、将来病気にならないとは限らない。

    Even if you are healthy now, there’s no guarantee you won’t get sick in the future.

    Word by Word: Now health even if, future illness become not that not limited.

    Here, it points out a future risk despite the current positive state.

  3. あの人が嘘をついていないとは限らない。

    It’s not impossible that that person is lying.

    Word by Word: That person lie telling not that not limited.

    This expresses skepticism toward someone who appears to be telling the truth.

  4. この薬が誰にでも効かないとは限らない。

    It's not necessarily the case that this medicine won't work for everyone.

    Word by Word: This medicine anyone for work not that not limited.

    A double negative suggesting there is still a possibility the medicine could be effective.

Common Mistakes

  • Confusing it with the simple partial negation '〜とは限らない'.

    金持ちが幸せではないとは限らない。
    金持ちが幸せとは限らない。

    〜とは限らない means 'not always [positive]'. 〜ないとは限らない means 'not always [negative]'. The incorrect example literally means 'It's not impossible for rich people to be unhappy,' which is the opposite of the intended 'Rich people aren't always happy.'

  • Using it for purely positive, happy possibilities.

    宝くじが当たらないとは限らない！
    宝くじが当たるかもしれない！

    While grammatically correct, 〜ないとは限らない is usually reserved for risks, errors, or skeptical exceptions. Using it for winning the lottery sounds overly logical and stiff; かもしれない is much more natural for hope.

How It Connects

Tap a pattern to see what it builds on and what it leads to.

〜ないとは限らないLevel 4Might

Learn This First

The pattern 〜ないとは限らない (might/it's not impossible) is a double negative construction. To understand it, you must first be comfortable with the plain negative form (ない form) and the standard expression 〜とは限らない (not necessarily). By combining these, you express that while something is unlikely, the negative outcome is not guaranteed, effectively meaning 'it might happen'.

Words in This Pattern

限る