The certainty scale at a glance
The easiest way to learn these adverbs is as a scale. The certainty levels below are only a rough guide, since real people use them loosely, but the order is reliable and it helps you choose the right word under pressure.
Notice that the adverbs usually pair with particular endings. Moshikashitara wants kamo shirenai; tabun and osoraku like deshō, darō or to omou; kitto can take deshō or stand with a plain statement; kanarazu and zettai usually take a plain, confident ending.
| Adverb | Rough certainty | Typical partner ending | Feel |
|---|---|---|---|
| もしかしたら | Low: it's possible | かもしれない | Tentative |
| たぶん | Moderate: probably | でしょう / と思う | Everyday, neutral |
| おそらく | Moderate to high | でしょう / と思われる | Formal, cautious |
| きっと | High: I'm sure | でしょう / plain form | Confident, warm |
| 必ず | Very high: without fail | plain form / ます | Firm, objective |
| 絶対 | Very high: absolutely | plain form / ない | Emphatic, casual |
Tabun: the everyday "probably"
たぶん (tabun) is the most common way to say probably. It works in casual and polite speech, and people use it constantly, sometimes several times in one conversation. It is usually written in hiragana, though the kanji 多分 is also common.
Tabun often pairs with deshō, darō or to omou, but in casual speech it can simply sit in front of a plain sentence: tabun ame, probably rain. It also works as a one-word reply, which is useful but needs care, as we will see.
| Japanese | Romaji | Meaning |
|---|---|---|
| たぶん大丈夫だと思います。 | Tabun daijōbu da to omoimasu. | I think it's probably fine. |
| 明日はたぶん雨でしょう。 | Ashita wa tabun ame deshō. | It will probably rain tomorrow. |
| たぶん、もう帰ったよ。 | Tabun, mō kaetta yo. | They've probably gone home already. |
| たぶん行けると思う。 | Tabun ikeru to omou. | I think I can probably make it. |
| たぶんね。 | Tabun ne. | Probably, yeah. |
Osoraku: formal and cautious
おそらく (osoraku), sometimes written 恐らく, is close to tabun in meaning but sounds more formal and considered. You will hear it on the news, in presentations and in careful business explanations, where it often introduces a prediction someone might not want to hear.
Because the kanji 恐 is linked to fear, some people feel osoraku suits negative outcomes, and it does often appear with them. It is not limited to bad news, though; it simply sounds measured and serious.
| Japanese | Romaji | Meaning |
|---|---|---|
| おそらく間に合わないでしょう。 | Osoraku maniawanai deshō. | In all likelihood it won't be ready in time. |
| おそらく原因は設定だと思われます。 | Osoraku gen'in wa settei da to omowaremasu. | The cause is most likely the settings. |
| おそらく明日の午後になるかと思います。 | Osoraku ashita no gogo ni naru ka to omoimasu. | It will most likely be tomorrow afternoon. |
| 台風はおそらく週末に上陸するでしょう。 | Taifū wa osoraku shūmatsu ni jōriku suru deshō. | The typhoon will most likely make landfall at the weekend. |
Kitto: confident, and often kind
きっと (kitto) expresses strong confidence that comes from the speaker's own feeling or judgement. It often carries warmth: hope, trust or encouragement. Kitto daijōbu, I'm sure it'll be fine, is one of the most comforting short lines in Japanese.
Because kitto is about the speaker's inner conviction, it suits predictions, wishes and promises made with feeling: kitto mata aimashō, let's be sure to meet again. It is less suited to objective facts, rules or schedules, where kanarazu sounds more natural.
| Japanese | Romaji | Meaning |
|---|---|---|
| きっと大丈夫だよ。 | Kitto daijōbu da yo. | I'm sure it'll be fine. |
| きっと合格できるよ。 | Kitto gōkaku dekiru yo. | I'm sure you'll pass. |
| 彼はきっと喜ぶでしょう。 | Kare wa kitto yorokobu deshō. | I'm sure he'll be delighted. |
| きっとまた会えるよね。 | Kitto mata aeru yo ne. | We'll meet again, won't we. |
| きっと来てね。 | Kitto kite ne. | Be sure to come, OK? |
Kitto is great for encouragement, but it can feel hollow if the situation really is uncertain. When a friend is worried about something serious, a line that acknowledges the worry first often lands better than an instant kitto daijōbu.
Kanarazu and zettai: no room for doubt
必ず (kanarazu) means without fail or always. It is firm and fairly objective, so it fits rules, habits, schedules and professional promises: kanarazu kakunin shite kudasai, please be sure to check. In business, it is the natural choice for commitments.
絶対 (zettai), often 絶対に, means absolutely. It is emphatic and emotional, and very common in casual speech, especially with negatives: zettai iya, absolutely not. It also works for strong personal promises between friends, but in formal settings it can sound over-confident or a little childish.
| Japanese | Romaji | Meaning |
|---|---|---|
| 毎朝必ずコーヒーを飲みます。 | Maiasa kanarazu kōhī o nomimasu. | I always have coffee every morning. |
| 必ずご連絡いたします。 | Kanarazu go-renraku itashimasu. | I will be sure to contact you. |
| 提出前に必ず確認してください。 | Teishutsu mae ni kanarazu kakunin shite kudasai. | Please be sure to check before submitting. |
| 絶対行く！ | Zettai iku! | I'm definitely going! |
| それは絶対に無理です。 | Sore wa zettai ni muri desu. | That's absolutely impossible. |
| 絶対言わないでね。 | Zettai iwanaide ne. | Don't you dare tell anyone. |
The low end: moshikashitara, tashika and masaka
Below tabun sit words for weaker possibilities. もしかしたら (moshikashitara), or the slightly more casual もしかして and ひょっとしたら, introduce something that might be true, usually with kamo shirenai.
確か (tashika) is different: it means "if I remember correctly" and is perfect for facts you are fairly but not fully sure of. まさか (masaka) points the other way, expressing disbelief that something could be true.
| Japanese | Romaji | Meaning |
|---|---|---|
| もしかしたら遅れるかもしれません。 | Moshikashitara okureru kamo shiremasen. | I might possibly be late. |
| ひょっとしたら、もう知ってる？ | Hyotto shitara, mō shitteru? | Do you happen to know already? |
| 確か三時からだったと思います。 | Tashika sanji kara datta to omoimasu. | If I remember right, it starts at three. |
| まさか、そんなはずないよ。 | Masaka, sonna hazu nai yo. | No way, that can't be right. |
Tashika is extremely useful at work. Tashika ... datta to omoimasu signals that you believe something but have not rechecked it, which is honest and polite.
Talking about other people's plans
Japanese is careful about claiming to know what is inside someone else's head. Saying kare wa kitto kuru with complete confidence is natural as a prediction, but for plans that are really another person's decision, it is often better to add a softer ending that shows you are guessing.
This is where the adverbs combine with endings such as deshō, to omou, rashii and mitai. The adverb sets the strength; the ending shows the source. Our guides to deshō and darō and to kamo shirenai and ni chigainai go deeper into those endings.
| Japanese | Romaji | Meaning |
|---|---|---|
| 田中さんはたぶん来ると思います。 | Tanaka-san wa tabun kuru to omoimasu. | I think Tanaka-san will probably come. |
| 部長はきっと賛成してくれるでしょう。 | Buchō wa kitto sansei shite kureru deshō. | I'm sure the manager will agree. |
| たぶん休みみたいです。 | Tabun yasumi mitai desu. | It seems they're probably off today. |
Common mistakes and how to fix them
- Answering a yes-or-no question with a bare tabun when you mean yes. Add detail: tabun ikeru, demo hachiji goro ni naru kamo, I can probably go, but it might be around eight.
- Using zettai for business promises. Switch to kanarazu, which sounds reliable rather than emotional.
- Using kitto for timetables and rules. Kitto densha wa hachiji ni tsuku sounds like wishful thinking; use tabun or state the fact.
- Stacking certainty that contradicts itself, such as zettai ... kamo shirenai. Match a strong adverb with a confident ending and a weak adverb with a tentative one.
- Forgetting that tabun is fine in polite speech. Learners sometimes switch to osoraku everywhere and sound like a news broadcast.