なくはない / なくもない

The expressions なくはない and なくもない are used to express a weak affirmative by means of double negation – literally "it's not that it isn't" or "it's not that there isn't." Rather than saying something directly, the speaker hedges, suggesting that something is partially true, somewhat possible, or not entirely absent. The nuance is similar to English "it's not that I don't…" or "I wouldn't say I can't…"

Both forms are largely interchangeable, though なくもない can sound slightly softer or more noncommittal than なくはない.

Formation

These expressions attach to the negative stem of verbs, adjectives, and nouns:

• Verb: V[ない form] → drop ない → なくはない / なくもない

  いかなく行かなくはないけど、あまりきがすすまない気が進まない。

  It's not that I won't go, but I'm not really in the mood.

• い-adjective: drop い → くなくはない / くなくもない

  このりょうり料理はおいしくなくもない。

  It's not that this dish isn't tasty (but it's not great either).

• な-adjective / Noun: ～でなくはない / ～でなくもない

  かれ彼のいけん意見がただしい正しいといえなく言えなくもない。

  You could say his opinion is correct (it's not that you couldn't).

Nuance

The key nuance is reluctant or partial acknowledgment. The speaker admits that something is true or possible to some degree, but implies reservations, conditions, or lack of enthusiasm. It is often followed by a clause introduced by けど or が that explains the reservation.

Common mistakes

Be careful not to confuse this with the simple negative ない. The double negation here creates a weak positive, not a negative meaning. Also note that this pattern is used in spoken or written discourse to express nuanced opinions – it is not used for simple factual statements.