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N4Lesson notes · Sep 30, 2026

Definitely and never in Japanese: 絶対ぜったい, 必かならず, 決けっして — which ones can go negative

"Definitely" is 絶対ぜったい or 必かならず, and the difference is that 絶対ぜったい can sit in a positive or a negative sentence (絶対行ぜったいいく / 絶対行ぜったいいかない), while 必かならず goes with positive actions (必かならず行いく) and with negative requests like 必かならず忘わすれないでください, but not with "I will never" (必かならず行いかない).

English gets by with two words, "definitely" and "never," that look like opposites. Japanese splits the territory into several words, and each one has a rule about whether it wants a positive verb or a negative one. Learners usually run into this when they try 必かならず+ない and get a strange look. This article sorts out which word goes where, so you can pick the right one on the first try.

The basics

How do you say "definitely" in Japanese?

Use 絶対ぜったい (ぜったい) when you want a strong, personal "for sure," and 必かならず (かならず) when you mean "without fail," usually about a promise, a rule, or something that reliably happens.

明日あした、絶対行ぜったいいく。 — I'll definitely go tomorrow. (casual, personal determination) 明日あしたは必かならず来きてください。 — Please be sure to come tomorrow. (polite request, a rule or a firm ask)

Both mean "definitely," but the feel is different. 絶対ぜったい is about how strongly you feel. 必かならず is about the thing being certain to happen, or the person being certain to do it. That is why 必かならず shows up on notices, instructions, and promises. If you want to see how promises are made in full, our promise in Japanese article goes deeper.

Which one can go with a negative verb?

絶対ぜったい can. 必かならず cannot, at least not for "I will never." 絶対ぜったい+negative means "absolutely not" or "no way, never."

あんなところ、絶対行ぜったいいかない。 — I'm never going to a place like that. (casual, firm refusal) 絶対ぜったいにしません。 — I will absolutely not do it. (polite, strong denial)

If you try 必かならず行いかない to mean "I'll never go," it will sound wrong to most listeners. 必かならず is a word for things that will happen. Reach for 絶対ぜったい (or 決けっして, below) when you want the negative.

Is 絶対ぜったいに different from 絶対ぜったい?

Not by much. 絶対ぜったいに adds に, which makes the sentence a little more formal or emphatic, and you will often hear it with a negative command: 絶対ぜったいに忘わすれないでください ("Please never forget"). In casual speech the に is very often dropped: 絶対行ぜったいいく、絶対ぜったいやる.

What is the "never" family, all at once?

Here is the map. The thing to watch is whether the verb at the end is positive or negative. Each word below pairs with a different kind of "never."

Word Goes with Rough meaning Example
絶対ぜったい Positive or negative definitely / absolutely not 絶対行ぜったいいく / 絶対行ぜったいいかない
必かならず Positive, or a negative request without fail, be sure to 必かならず連絡れんらくします / 必かならず忘わすれないでください
決けっして Negative only never, by no means (formal) 決けっして忘わすれません
一度いちども Negative not even once (experience) 一度いちども行いったことがない
全然ぜんぜん Negative (traditionally) not at all 全然ぜんぜんわからない
二度にどと Negative never again 二度にどと行いかない
きっと Positive or negative surely, most likely きっと来くる / きっと来こない

You do not need to memorize all seven at once. Start with 絶対ぜったい and 必かならず. Then learn the "never" words by the situation they describe, which is what the next section covers.

Beyond the basics

What does 決けっして mean, and when do you use it?

決けっして (けっして) means "never" or "by no means," and it is only used with a negative. It has a formal, slightly written feel, so you hear it in speeches, promises, and serious statements more than in casual chat.

あなたのことは決けっして忘わすれません。 — I will never forget you. (polite, emotional and formal) これは決けっして簡単かんたんなことではありません。 — This is by no means an easy thing. (polite, formal, explaining or warning)

Compared with 絶対ぜったい+ない, 決けっして+ない sounds calmer and more dignified. 絶対行ぜったいいかない is a punchy refusal you can say to a friend. 決けっして行いきません is the version you would hear from someone making a solemn statement. Both are grammatical. The choice is about tone.

How do you say "I've never done that"?

For experience, use 一度いちども (いちども) plus a negative. This is the "never" of your life so far, and it works with 〜たことがない.

日本にほんには一度いちども行いったことがない。 — I've never been to Japan. (casual, experience) 納豆なっとうは一度いちども食たべたことがありません。 — I've never eaten natto. (polite, experience)

一度いちども means "not even one time," so it needs a negative verb. The grammar behind 〜たことがある is in our 〜たことがあります article, and that page is the right place to start if "have you ever" still feels shaky.

A small note: 絶対ぜったい does not give the plain "never in my life" count. 絶対行ぜったいいったことがない means "I'm certain I have never been", a statement of confidence. For the plain count, use 一度いちども.

What is the difference between 全然ぜんぜん and 決けっして?

全然ぜんぜん (ぜんぜん) means "not at all" and is traditionally used with a negative: 全然ぜんぜんわからない ("I don't understand at all"). In casual modern speech, you will also hear it with a positive word, like 全然ぜんぜんいい ("that's totally fine"). Some people still consider that use casual or non-standard, so as a learner it is safer to keep 全然ぜんぜん with negatives in writing and formal situations.

この問題もんだい、全然ぜんぜんわからない。 — I don't get this problem at all. (casual) 全然ぜんぜん大丈夫だいじょうぶだよ。 — It's totally fine. (very casual, positive use you will hear in speech)

The difference from 決けっして: 全然ぜんぜん talks about degree ("zero amount of it"), while 決けっして talks about a firm "never" as a rule or resolve. 全然ぜんぜんわからない says how much you understand. 決けっしてわからない would sound strange for that, because it is not an emphatic promise.

How do you say "never again"?

二度にどと (にどと) plus a negative means "never again." It refers to a repeat, and it usually carries emotion: regret, anger, or a serious vow.

あの店みせには二度にどと行いかない。 — I'm never going to that shop again. (casual, annoyed) 二度にどとこんなことはしません。 — I will never do this again. (polite, apology)

二度にどと is very natural in apologies and promises to change. If your "never" has an implied "once was enough," 二度にどと is the word. For "again" in the neutral sense, see the again article.

How is きっと different from 絶対ぜったい?

きっと (surely, most likely) is confident, but it is a prediction rather than a promise. It sounds softer than 絶対ぜったい. If you say きっと来くるよ, you are saying "I'm sure they'll come." If you say 絶対ぜったい来くるよ, you are pushing harder, as if you are betting on it.

きっとうまくいくよ。 — It'll surely go well. (casual, encouraging) 絶対ぜったいうまくいくよ。 — It will definitely go well. (casual, stronger, almost insisting)

きっと belongs with words like たぶん and かもしれない on the certainty scale. Our たぶん、でしょう article lines them up from most to least sure.

Do 絶対ぜったい and 必かならず ever get mixed up in real speech?

Yes, and it is normal. In casual speech, people use 絶対ぜったい in places where a textbook would write 必かならず, because it is punchier. The reverse is less common: 必かならず tends to stay in writing, announcements, and polite speech. If you are not sure, 絶対ぜったい is the more flexible word in conversation.

A related point about frequency: 必かならず is not the same as 毎回まいかい or いつも. Those say how often, while 必かならず says no exceptions. For the frequency set, see our Japanese frequency adverbs article.

Will overusing 絶対ぜったい sound childish?

It can. 絶対ぜったい is the default word for strong feelings, so a speaker who says 絶対ぜったい in almost every sentence can come across as a bit dramatic or emphatic, the way English "totally" and "literally" can wear out when they are in every line. This depends a lot on the speaker and the situation, and it is not a fixed rule. If you want a calmer tone, mix in きっと, ぜひ, or 決けっして where they fit.

In anime you will hear 絶対ぜったい constantly, often in dramatic moments like a character vowing not to forgive or not to give up. That is a good listening habit to build: notice whether the sentence after 絶対ぜったい ends in a positive or a negative.

Common mistakes

  • Using 必かならず with a negative to mean "never." 必かならず行いかない is not the natural way to say "I'll never go." Use 絶対行ぜったいいかない, or 決けっして行いきません in a formal register.
  • Using 決けっして with a positive verb. 決けっして行いく is wrong. 決けっして needs a negative: 決けっして行いきません.
  • Using 絶対ぜったい for the plain "I've never been." 絶対ぜったい adds "I'm sure"; for life experience use 一度いちども+ことがない: 一度いちども行いったことがない.
  • Confusing 必かならずしも with 必かならず. 必かならずしも〜ない means "not necessarily." 高たかいものが必かならずしもいいわけではない means "expensive things are not necessarily good." It is a different word, not the negative of 必かならず.
  • Treating きっと as a promise. きっと is a confident guess. If you need a firm promise, use 必かならず or 絶対ぜったいに.

Practice

Build each answer before opening it. Questions 3 and 4 are a pair, the same idea going in opposite directions.

1. Say "I'm definitely going tomorrow" in casual Japanese.

Show answer

明日あした、絶対行ぜったいいく — 絶対ぜったい is the personal, casual "definitely," and it works with a positive verb.

2. Say "Please be sure to come" politely.

Show answer

必かならず来きてください — 必かならず is for a firm request or rule with a positive action.

3. Say "I'm never going to that place" in casual Japanese.

Show answer

あんなところ、絶対行ぜったいいかない — 絶対ぜったい can pair with a negative verb for "never / no way." This is the pair to question 4.

4. Why is 必かならず行いかない a poor way to say "I'll never go"?

Show answer

必かならず is for things that will happen, so it pairs with positive actions. For "never," switch to 絶対ぜったい or 決けっして.

5. Say "I will never forget you" in a formal, emotional tone.

Show answer

決けっして忘わすれません — 決けっして is formal and negative-only, so it fits a solemn promise.

6. Say "I've never been to Japan."

Show answer

日本にほんには一度いちども行いったことがない — 一度いちども means "not even once" and describes experience, combined with ことがない.

7. Say "I'm never going to that shop again."

Show answer

あの店みせには二度にどと行いかない — 二度にどと means "never again" and carries the feeling of "once was enough."

8. Which is more of a confident guess and less of a promise: きっと or 絶対ぜったい?

Show answer

きっと — it is a confident prediction and sounds softer. 絶対ぜったい pushes harder, as if you were insisting.

9. What does 必かならずしも高たかくない mean?

Show answer

"Not necessarily expensive" — 必かならずしも〜ない is its own pattern meaning "not necessarily," not the negative of 必かならず.

Make a few promises and flat refusals in a trial lesson and watch which of 絶対ぜったい, 必かならず and 決けっして can take a negative verb.

FAQ

Is 絶対ぜったい rude? No. It is a normal, strong word. It can sound emphatic or dramatic if you use it in nearly every sentence, so vary it with きっと or ぜひ.

Can I say 絶対ぜったいに in casual speech? Yes, but the に is often dropped in casual speech. 絶対ぜったいやる and 絶対ぜったいにやる both work, with the version that has に sounding a little more emphatic.

Which is more polite, 必かならず or 絶対ぜったい? 必かならず fits polite and written contexts better, such as notices and instructions. 絶対ぜったい is at home in casual conversation, and 絶対ぜったいに fits polite speech when you want strong emphasis.

Can 全然ぜんぜん be used with a positive? In casual speech you will hear it, as in 全然ぜんぜんいい. As a learner, it is safer to use 全然ぜんぜん with negatives, especially in writing.

What is the difference between 決けっして and 二度にどと? 決けっして means "never" as a firm rule or resolve. 二度にどと means "never again," so it refers to something that has already happened once.

Vocabulary from this article

Tap the block to select all of it, then copy. In Anki: File → Import, note type Basic, separator Tab — the first column becomes the front, the second the back.

絶対	ぜったい — definitely, absolutely
必ず	かならず — without fail, be sure to
決して	けっして — never, by no means (with negative)
一度も	いちども — not even once
全然	ぜんぜん — not at all
二度と	にどと — never again
きっと	きっと — surely, most likely
必ずしも	かならずしも — not necessarily (with negative)
忘れる	わすれる — to forget
簡単	かんたん — easy, simple

I'm Yuuki, a Japanese teacher based in Tokyo. I've taught on italki as a Top 1% teacher and watched over 1,500 anime, so most of the example sentences on this blog come from lines I've actually heard students ask about — including this one, where 必かならず and 絶対ぜったい get swapped in almost every learner's first months. For practice with feedback, Book a trial lesson · $13, or work through Japanese practice exercises first.

Sources: the author's own lessons and standard reference grammars.

More drills like the ones above, plus a timed JLPT-style mock test: Practice · N4 · Read something at this level: JLPT N4 stories with audio

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