決して〜ない: 'Never' / 'By No Means'
What it means
決して is an adverb that intensifies a negative. On its own it doesn't mean much; it leans forward and waits for the negative ending to land, then drives it home. The result is the English "never," "by no means," "absolutely not," or "on no account."
Use it for two closely related feelings:
- Firm resolve — a promise to yourself or someone else: 決してあきらめない ("I will never give up").
- Strong denial — knocking down an idea flatly: 決して簡単ではない ("it's by no means easy").
ヤッタンは決してあきらめない。
ヤッタンは けっして あきらめない。
Yattan will never give up.
Resolve — a firm personal commitment.
この約束は決して忘れません。
この やくそくは けっして わすれません。
I will never forget this promise.
Polite negative 忘れません completes the pattern.
先生は、この試験は決して簡単ではないと言った。
せんせいは、この しけんは けっして かんたんでは ないと いった。
The teacher said this exam is by no means easy.
Denial — knocking down the idea that it's easy.
How to form it
決して sits before the predicate, and the predicate must end in a negative form. The negative can be a verb, an い-adjective, or a な-adjective/noun.
| Predicate type | Pattern | Example |
|---|---|---|
| Verb (plain) | 決して + 〜ない | 決して言わない (will never say) |
| Verb (polite) | 決して + 〜ません | 決して言いません |
| い-adjective | 決して + 〜くない | 決して安くない (by no means cheap) |
| な-adj / noun | 決して + 〜ではない | 決して簡単ではない |
| Past negative | 決して + 〜なかった | 決して許さなかった (never forgave) |
The one rule that matters: no negative, no 決して. Pairing it with a plain affirmative verb is ungrammatical (see Common mistakes).
More examples
モチは決してうそをつかない人だ。
モチは けっして うそを つかない ひとだ。
Mochi is someone who never tells a lie.
決して inside a relative clause modifying 人.
弟は決して泣かなかった。
おとうとは けっして なかなかった。
My little brother never cried.
Past negative 泣かなかった.
あなたのことは決して悪く言いません。
あなたの ことは けっして わるく いいません。
I will never speak ill of you.
A reassuring promise — common use of the resolve sense.
この道は決して安全だとは言えない。
この みちは けっして あんぜんだとは いえないと。
This road can by no means be called safe.
決して often pairs with 〜とは言えない for emphatic denial.
Register and nuance
決して is somewhat formal and emphatic. It belongs in earnest promises, warnings, official notices ("決して立ち入らないでください" — "on no account enter"), and confident assertions. In very casual chat you'd more often hear 絶対 (ぜったい), which is the everyday cousin: 絶対あきらめない. 決して carries a touch more weight and formality.
Because it expresses a categorical "never," it pairs naturally with strong statements of principle, prohibition, or determination — not with mild or hedged ones.
決して vs めったに vs 全然
These three all live near negatives, but they mean different things:
- 決して〜ない = never, by no means — a categorical, 0% denial or firm resolve. It's about certainty/determination, not counting: 決して行かない ("I will never go").
- めったに〜ない = rarely, hardly ever — a statement about frequency. It's not zero; it just doesn't happen often: めったに行かない ("I hardly ever go").
- 全然〜ない = not at all — emphatic degree, often about a current state or amount: 全然おもしろくない ("not interesting at all"). See 〜全然.
So 決して is the "absolutely not / never, ever" of resolve and denial; めったに measures how often; 全然 measures how much. Swapping them changes the meaning, not just the strength.
Common mistakes
- Pairing 決して with an affirmative verb. This is the big one. 決して needs a negative: say 決して忘れない ("I'll never forget"), never ✗決して忘れる. If your sentence ends affirmatively, 決して cannot be there.
- Using it for frequency. "I rarely eat meat" is a frequency statement → use めったに食べない, not 決して食べない (which would mean "I will never eat meat," a vow).
- Treating it like casual 全然. 全然 modifies degree ("not at all"). For "it's not interesting at all," use 全然おもしろくない, not 決しておもしろくない.
- Forgetting it's formal/emphatic. Don't sprinkle 決して into light, everyday remarks where 絶対 or a plain negative fits better; it can sound overly dramatic.
Quick recap
- 決して = never / by no means / absolutely not — always with a negative predicate.
- Two flavors: firm resolve (決してあきらめない) and strong denial (決して簡単ではない).
- No negative ending = ungrammatical; that's the #1 mistake.
- Register is formal/emphatic; casual speech often uses 絶対.
- Contrast: めったに〜ない = rarely (frequency); 全然〜ない = not at all (degree).
Your turn
Choose the sentence where 決して is correctly paired with a negative.
Start the 5-question drill →Take the full N3 決して〜ない drill →
Frequently asked questions
Does 決して always need a negative?
Yes. 決して is an adverb that intensifies a negative predicate, so it must be followed by a negative form (〜ない, 〜ません, 〜ではない, etc.). Pairing it with a plain affirmative verb is ungrammatical.
What's the difference between 決して and めったに?
決して〜ない means 'never, by no means' — a categorical denial or firm resolve. めったに〜ない means 'rarely, hardly ever' and is about frequency: the action still happens occasionally.
Is 決して the same as 全然?
No. 全然〜ない means 'not at all' and modifies degree (全然おもしろくない). 決して expresses absolute denial or determination ('never'). They aren't interchangeable.
How formal is 決して?
It's somewhat formal and emphatic — at home in promises, warnings, and official notices. In casual conversation, 絶対 (ぜったい) is the everyday equivalent.