22 Japanese ways to say “Definitely”

When you want to express certainty in Japanese, there are plenty of warm, casual, and formal ways to say “definitely.”

From everyday conversations to more polite speech, each phrase carries its own nuance and vibe.

Learning these variations not only boosts your fluency but also helps you connect better with different people and settings.

Whether you’re assuring a friend or confidently making a statement, this list has got you covered with 22 natural ways to say “definitely” in Japanese.

Ready to sound more like a native? Let’s dive in and explore these expressions together.

Plus, I’ll sprinkle in some handy tips and links to resources that can help you practice with confidence.

Understanding Certainty in Japanese

Expressing certainty in Japanese can be subtle, depending on the context and your relationship with the listener.

Some phrases are casual and friendly, perfect for chatting with friends, while others are more formal and respectful for business or polite conversations.

Knowing when and how to use these expressions will make your Japanese sound natural and clear.

If you want a solid foundation, a great Japanese phrasebook can be a wonderful tool to start practicing these phrases in real conversations.

With practice, these words will flow naturally and boost your confidence.

Let’s begin with some casual, easy-going expressions.

Part 1: Casual Suggestions

1. ぜったいに (Zettai ni) – “Definitely, without a doubt.”

This is the most straightforward way to say “definitely” in Japanese.

“ぜったい” (zettai) means “absolute” or “certain,” and “に” (ni) is a particle that emphasizes the word.

It’s perfect for everyday use when you want to be clear and confident.

Use it when you want to leave no room for doubt.

You might hear it a lot in casual conversations or even in dramas.

Once you start using “zettai ni,” you’ll notice it’s a go-to for expressing strong certainty.

2. 間違いない (Machigai nai) – “No mistake about it.”

This phrase literally means “there is no mistake,” so it’s a strong way to say “definitely.”

It’s common in both casual and semi-formal settings and sounds very natural.

Try saying “Machigai nai” when you’re 100% sure about something.

It’s often used in conversations to reassure or confirm facts.

Be careful not to use it if there’s any doubt, as it implies complete certainty.

Example: “このやり方で間違いないよ。” (Kono yarikata de machigai nai yo.) – “There’s definitely no mistake with this method.”

3. 本当に (Hontō ni) – “Truly, really.”

“本当に” means “really” or “truly,” and it’s used to emphasize sincerity or certainty.

It’s casual but polite enough for everyday conversations.

Use it when you want to stress that something is definitely true.

This phrase also works well to show emotion and honesty.

It can be paired with other expressions for added effect.

Example: “本当に行くよ！” (Hontō ni iku yo!) – “I’m definitely going!”

4. 絶対 (Zettai) – “Absolutely.”

“絶対” is a short, strong word that means “absolutely” or “definitely.”

It’s often used alone or with particles like “に” (ni) or “だ” (da) to make it more emphatic.

It’s a popular choice for expressing certainty in casual speech.

Just be aware it sounds strong and confident, so use it when you really want to be clear.

Try “絶対行く！” (Zettai iku!) to say “I’m definitely going!”

Perfect for guaranteeing your plans or promises.

5. もちろん (Mochiron) – “Of course, definitely.”

“もちろん” means “of course,” and it’s a friendly, confident way to say “definitely.”

Use it when affirming something expected or agreed upon.

It’s very common in casual conversations and sounds natural.

It works well when you want to reassure someone positively.

Example: “明日来る？“ “もちろん！” (Ashita kuru? “Mochiron!”) – “Are you coming tomorrow?” “Definitely!”

Try this one to sound approachable and certain.

6. 絶対にそうだよ (Zettai ni sō da yo) – “That’s definitely right.”

This phrase is a bit longer but very clear and emphatic.

“絶対に” (zettai ni) means “definitely,” “そうだ” (sō da) means “that’s right,” and “よ” (yo) adds emphasis.

It’s great for confirming facts or opinions with conviction.

Use it to sound confident and sure.

It’s more casual but still polite enough for friends or colleagues.

Example: “彼が犯人だって？ 絶対にそうだよ。” (Kare ga hannin datte? Zettai ni sō da yo.) – “He’s the culprit? Definitely.”

7. 絶対に間違いない (Zettai ni machigai nai) – “Absolutely no mistake.”

This is a super strong statement combining two phrases for certainty.

It literally means “there is absolutely no mistake.”

Use it when you want to be very sure and leave no doubt.

It’s common in serious conversations or arguments.

Try it when you want to sound very convincing.

Example: “この証拠は絶対に間違いない！” (Kono shōko wa zettai ni machigai nai!) – “This evidence is definitely not wrong!”

8. 確かに (Tashika ni) – “Certainly, surely.”

“確かに” means “certainly” or “surely,” often used to agree or confirm something.

It’s polite but casual, fitting for many situations.

Use it to acknowledge truth or agreement confidently.

It can soften your statement while still showing certainty.

Example: “確かに彼は優秀ですね。” (Tashika ni kare wa yūshū desu ne.) – “He is definitely talented.”

Great for polite affirmation.

Part 2: Polite & Formal Suggestions

9. 間違いありません (Machigai arimasen) – “There is no mistake.” (polite)

This is the polite form of “間違いない.”

“ありません” is the formal negative of “aru” (to be/exist), making it respectful.

Use this in business, presentations, or formal conversations to express certainty.

It’s a safe choice when you want to sound professional.

Example: “この資料に間違いありません。” (Kono shiryō ni machigai arimasen.) – “There is definitely no mistake in this document.”

Try this phrase to impress in formal settings.

10. 確実に (Kakujitsu ni) – “Certainly, reliably.” (formal)

“確実に” means “certainly” or “surely,” used in formal speech to express reliability or assurance.

It’s often used in official documents or speeches.

Try it when you want to sound factual and professional.

Example: “プロジェクトは確実に成功します。” (Purojekuto wa kakujitsu ni seikō shimasu.) – “The project will definitely succeed.”

Keep this in your polite vocabulary for confident statements.

11. 当然です (Tōzen desu) – “Naturally, of course.” (formal)

“当然” means “natural” or “obvious,” and “です” makes it polite.

Use this phrase to say “definitely” in a formal, respectful way.

It’s often used to affirm something expected or logical.

Example: “それは当然の結果です。” (Sore wa tōzen no kekka desu.) – “That is definitely the expected result.”

Use it to sound respectful and confident.

12. 間違いございません (Machigai gozaimasen) – “There is absolutely no mistake.” (very formal)

This is the very polite version of “間違いありません.”

“ございません” is a humble and respectful negative form, perfect in customer service or formal speeches.

Use it to emphasize certainty in respectful contexts.

Example: “お伝えした内容に間違いございません。” (Otsutaeshita naiyō ni machigai gozaimasen.) – “There is definitely no mistake in the information I gave you.”

Perfect for business or formal emails.

13. 確かです (Tashika desu) – “It is certain.” (polite)

A polite and simple way to say “definitely” or “certain.”

Use it in conversations where you want to confirm something politely.

It’s slightly softer than some other expressions, making it versatile.

Example: “その情報は確かです。” (Sono jōhō wa tashika desu.) – “That information is definitely correct.”

Great for polite assurances.

14. 確信しています (Kakushin shiteimasu) – “I am confident.” (formal)

“確信” means “confidence” or “conviction,” and “しています” is the polite present continuous form of “to do.”

Use this phrase to express strong personal certainty or belief.

It’s formal and respectful, perfect for speeches or serious conversations.

Example: “この計画は成功すると確信しています。” (Kono keikaku wa seikō suru to kakushin shiteimasu.) – “I am definitely confident this plan will succeed.”

Use it to sound professional and sure of yourself.

15. 間違いなく承知しました (Machigai naku shōchi shimashita) – “I definitely understood.” (formal)

This phrase combines strong certainty with polite acknowledgement.

“承知しました” is a formal way to say “I understand” or “acknowledged.”

Use it in emails or conversations to confirm understanding with certainty.

Example: “ご指示の件、間違いなく承知しました。” (Go shiji no ken, machigai naku shōchi shimashita.) – “I definitely understood your instructions.”

Useful in work communication.

16. 間違いないと信じています (Machigai nai to shinjiteimasu) – “I believe there’s no mistake.” (formal)

This phrase adds a belief or trust element to certainty.

“信じています” means “I believe,” making the certainty personal yet polite.

It’s perfect for expressing respectful confidence.

Example: “この報告は間違いないと信じています。” (Kono hōkoku wa machigai nai to shinjiteimasu.) – “I definitely believe this report is correct.”

Good for formal conversations with a gentle touch.

Part 3: Very Casual / Native-like Expressions

17. 絶対だよね (Zettai da yo ne) – “Definitely, right?” (casual)

This is a very casual, conversational way to say “definitely.”

“だよね” adds a friendly, confirming tone.

Use this among friends for agreement or reassurance.

It’s natural and sounds native-like.

Example: “あの映画、最高だったよね。絶対だよね！” (Ano eiga, saikō datta yo ne. Zettai da yo ne!) – “That movie was awesome, definitely!”

Great for casual chats and bonding moments.

18. まじで (Maji de) – “Seriously, definitely.” (slang)

“まじで” is slang for “seriously” or “really,” used by young people.

It’s very casual and adds emotion to certainty.

Use it in informal settings with friends.

Example: “まじで行くよ！” (Maji de iku yo!) – “I’m definitely going!”

Try it to sound more natural among younger speakers.

19. もちろんだよ (Mochiron da yo) – “Of course, definitely.” (casual)

A casual and friendly way to say “definitely.”

“だよ” makes it more personal and conversational.

Use it to assure friends or family confidently.

Example: “手伝ってくれる？“ “もちろんだよ！” (Tetsudatte kureru? “Mochiron da yo!”) – “Will you help me?” “Definitely!”

Simple and warm for everyday talks.

20. 間違いないっしょ (Machigai nai ssho) – “No doubt about it.” (very casual/slang)

This is a slangy, casual way to say “definitely.”

“っしょ” is a slangy ending that softens or confirms a statement.

Use it among close friends to sound natural and relaxed.

Example: “あれは間違いないっしょ！” (Are wa machigai nai ssho!) – “That’s definitely true!”

Perfect for informal conversations.

21. バッチリ (Bacchiri) – “Perfectly, definitely.” (casual)

“バッチリ” means “perfectly” or “spot on,” often used casually to mean “definitely.”

It’s cheerful and confident.

Use it when you want to say something will go perfectly or definitely happen.

Example: “準備はバッチリだよ！” (Junbi wa bacchiri da yo!) – “I’m definitely ready!”

Great for positive, casual assurance.

22. 断然 (Danzen) – “Absolutely, definitely.” (casual to formal)

“断然” is a strong word meaning “absolutely” or “by far.”

It can be used in casual or formal contexts depending on tone.

Use it to emphasize something is unquestionably true.

Example: “この方法が断然いい！” (Kono hōhō ga danzen ii!) – “This method is definitely the best!”

Use it to sound confident and assertive.

Concluding Thought

Exploring these 22 ways to say “definitely” in Japanese shows just how rich and nuanced the language is.

Whether casual or formal, each phrase lets you express certainty with personality and appropriateness.

Keep practicing, and soon you’ll express yourself with confidence in any situation—definitely!