ないとも限らない【ないともかぎらない】

The grammar pattern ないとも限らない expresses that something is not necessarily impossible – that is, there is a possibility it could happen, even if it seems unlikely. It conveys the nuance of "it's not necessarily the case that… won't" or "you can't rule out the possibility that…". It is used when the speaker wants to acknowledge a potential outcome that others might dismiss or overlook.

The structure is formed by attaching ないともかぎらない限らない to the verb stem (i.e., the negative stem without ない):

• Verb[ない form] + とも限らない

For example, おきる起きる → 起きない → 起きないとも限らない ("it's not necessarily the case that it won't happen").

Nuance

This pattern is used to express caution or warn about a possibility that should not be ignored. The speaker is typically urging someone to be prepared or to not be overconfident in a particular assumption.

It carries a hedging, cautious tone – the speaker doesn't assert that the thing will happen, only that it could. This makes it common in contexts involving risk assessment, warnings, and thoughtful deliberation.

Related patterns

• とは限らない means "not necessarily" and is used to deny a general assumption (e.g., たかい高いとはかぎらない限らない – "it's not necessarily expensive"). In contrast, ないとも限らない specifically addresses the possibility that something might happen despite expectations to the contrary.
• かもしれない ("might") is more neutral and common, while ないとも限らない emphasizes that one cannot rule out the possibility – a stronger, more deliberate phrasing typically found in formal or written Japanese.

Usage notes

• This pattern can also be used with い-adjectives and な-adjectives in their negative forms: やすくない安くないともかぎらない限らない ("it's not necessarily the case that it won't be cheap"), ひつよう必要でないともかぎらない限らない ("you can't say it won't be necessary").
• It is predominantly used in written language, news, essays, and formal speech, consistent with its N1 level.