How to tell them apart
ないことはない uses a double negative to admit that something is in fact the case, often softening it with a follow-up like but his blood pressure is a bit high. わけではない directly denies an implication or assumption, saying it is not that X is true. The test is whether you are confirming a negative question (元気じゃないことはない) or rejecting someone's inference (そういうわけではない). Swapping them sounds odd because ないことはない affirms while わけではない denies.
- ないことも / はない Use ないことはない when you confirm a negative question by admitting the positive, then add a reservation.
- わけではない Use わけではない when you deny an implied meaning or assumption that someone has drawn.
| Grammar point | Meaning | JLPT level |
|---|---|---|
| ないことも / はない naikotomo hanai | It isn't the case that... not; doesn't mean... not | N3 |
| わけではない wakedehanai | It is not the case that; not always so | N3 |
ないことも / はない naikotomo hanai
It isn't the case that... not; doesn't mean... not
ないことも / はない softens a negative statement, meaning something is not entirely the case. It attaches to the plain negative form of a verb, ない, optionally followed by わけ in the related pattern seen in the examples. It often appears as ないわけではない, a double negative that denies an absolute claim.
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数学はただ公式を暗記すればいいというものではない。
Mathematics is not just the memorization of formulas.
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たいしたことではないのに必要以上に物々しい言い方です。
It's much too pompous for such a trivial thing.
わけではない wakedehanai
It is not the case that; not always so
わけではない denies that something is universally or necessarily true, softening a statement to mean it does not always hold. It follows plain-form verbs and i-adjectives, na-adjectives and nouns with な, and often pairs with 必ずしも.
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貧しい人が必ずしも不幸なわけではないと言われている。
It is said that the poor are not always unhappy.
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世界一の金持ちでもすべてのものが買えるわけではない。
The richest man in the world cannot buy everything.
ないことも / はない and わけではない are both JLPT N3 grammar points that Japanese learners often mix up. This page compares them side by side on meanings, usage and example sentences, so you can tell them apart.