ないとも限らない|ないともかぎらない
- 1It cannot be ruled out that something will happen, so one had better be prepared.Ex. 1
- 2A warning that an undesirable result could occur if one is not careful.Ex. 2
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A somewhat formal, literal-sounding expression used in writing and in careful speech. It typically leads into a precaution or piece of advice with から or ので, or follows a condition such as 〜と or 〜ば. The possibility it raises is usually small: it says only that the outcome cannot be excluded, not that it is likely. Unlike とは限らない, which denies that something always holds, it affirms that something might happen.
Learners often misread the double negative: 来ないとも限らない means "he might come", not "he might not come".
Do not drop the ない before とも限らない: 来るとも限らない is a different sentence meaning "he may not come".
Note that the pattern usually concerns undesirable or unexpected events and naturally leads to a precaution or warning.
- ないものでもないN1「ないものでもない」centers on the speaker's grudging, hedged willingness or serves as a reserved evaluation, while「ないとも限らない」says an occurrence cannot be ruled out and is mostly used to prompt precautions; the two cannot be swapped when expressing willingness. The former generally attaches only to the ない-form of verbs.
- かねないN2「かねない」is used only for bad outcomes, directly stating that a certain cause or state may bring about a bad result; it attaches only to the verb stem (the ます-form minus ます), is neutral in register, and is common in conversation as well. When speaking of a bad outcome it can replace this pattern, but its note of warning is stronger.
- とは限らないN3「とは限らない」attaches to plain forms and means 'not necessarily...', with a neutral register, while this pattern attaches to the ない-form, leans written, and means 'it may also...'. When「とは限らない」takes the negative「〜ないとは限らない」, its meaning is close to this pattern.
- 恐れがあるN2「恐れがある」directly and objectively flags the danger of something bad happening and is common in news and weather forecasts; it is used only for bad things and takes「の」after a noun. 「ないとも限らない」only says the thing cannot be ruled out, with how likely it is depending on context.
- なくはないN2「なくはない」gives a hedged, partial affirmation of willingness, a state, or an evaluation ('it's not that... not...') and is often followed by a contrast, with a neutral register; 「ないとも限らない」says something may happen and urges precautions, leans written, and the two are not interchangeable.
- 〜なくもないN2「なくもない」is neutral in register and can also mean 'not impossible,' a sense close to this pattern; however, it can also grudgingly affirm one's own willingness or feelings (e.g.,「考えなくもない」), a usage this pattern does not have.
かねない and 恐れがある also point to a possible outcome, but かねない stresses a risk the speaker considers likely and 恐れがある is a formal, news-style statement of danger; とは限らない simply means "not necessarily". ないものでもない, なくはない and 〜なくもない express partial possibility or reluctant willingness ("it's not that I can't / won't") rather than warning that something may happen.
