Various degrees of certainty

In general, Japanese people don’t assert themselves of something unless they are absolutely sure that it is correct. This accounts for the incredibly frequent use of 「~と思う」 and the various grammatical expressions used to express specific levels of certainty. We will go over these expressions starting from the less certain to the most certain.

Using 「かもしれない」 to express uncertainty


  1. 多分 【た・ぶん】 – perhaps; probably
  2. 映画 【えい・が】 – movie
  3. 観る 【み・る】 (ru-verb) – to watch
  4. 彼 【かれ】 – he; boyfriend
  5. 学生 【がく・せい】 – student
  6. それ – that
  7. 面白い 【おも・し・ろい】 (i-adj) – interesting
  8. 先生 【せん・せい】 – teacher
  9. 退屈 【たい・くつ】 – boredom
  10. 食堂 【しょく・どう】 – cafeteria
  11. 行く 【い・く】 (u-verb) – to go
  12. 雨 【あめ】 – rain
  13. 試合 【し・あい】 – match, game
  14. 中止 【ちゅう・し】 – cancellation
  15. なる (u-verb) – to become
  16. この – this (abbr. of これの)
  17. 映画 【えい・が】 – movie
  18. ~回 【~かい】 – counter for number of times
  19. こと – event, matter
  20. ある (u-verb) – to exist (inanimate)
  21. あそこ – over there
  22. 代々木公園 【よ・よ・ぎ・こう・えん】 – Yoyogi park
  23. もう – already
  24. 逃げる 【に・げる】 (ru-verb) – to escape; to run away

「かもしれない」 is used to mean “maybe” or “possibly” and is less certain than the word 「多分」. It attaches to the end of a complete clause. For noun and na-adjective clauses, the declarative 「だ」 must be removed. It can also be written in kanji as 「かも知れない」 and you can treat it the same as a negative ru-verb (there is no positive equivalent) so the masu-form would become 「かもしれません」. In casual speech, it can be abbreviated to just 「かも」. There is also a very masculine version 「かもしれん」, which is simply a different type of negative verb.

Expressing uncertainty with 「かもしれない」

  • Simply attach 「かもしれない」 or 「かも知れない」 to the clause

    1. 映画観たかもしれない
    2. 学生かもしれない
    3. それ面白いかもしれない
  • Noun and na-adjective clauses must not use the declarative 「だ」

    1. 先生かもしれない → 先生かもしれない
    2. 退屈かもしれない → 退屈かもしれない
  • It can be abbreviated to just 「かも」 in casual speech

    1. 面白いかもしれない面白いかも


  1. スミスさんは食堂行ったかもしれません
    Smith-san may have gone to the cafeteria.
  2. 試合中止なるかもしれないね。
    The game may become canceled by rain, huh?
  3. この映画一回観たことあるかも
    I might have already seen this movie once.
  4. あそこ代々木公園かもしれない
    That might be Yoyogi park over there.
  5. もう逃げられないかもしれんぞ。
    Might not be able to escape anymore, you know.

Using 「でしょう」 to express a fair amount of certainty (polite)


  1. 多分 【た・ぶん】 – perhaps; probably
  2. 明日 【あした】 – tomorrow
  3. 雨 【あめ】 – rain
  4. 学生 【がく・せい】 – student
  5. これ – this
  6. どこ – where
  7. 行く 【い・く】 (u-verb) – to go
  8. 休む 【やす・む】 (u-verb) – to rest
  9. いただく (u-verb) – to receive; to eat; to drink (humble)

「でしょう」 is used to express a level of some certainty and is close in meaning to 「多分」. Just like 「~です/~ます」, it must come at the end of a complete sentence. It does not have any other conjugations. You can also replace 「~ですか」 with 「~でしょうか」 to make the question sound slightly more polite and less assuming by adding a slight level of uncertainty.


  1. 明日でしょう
    Probably rain tomorrow too.
  2. 学生さんでしょうか。
    Are (you) student?
  3. これからどこ行くでしょうか?
    Where (are you) going from here?

If you want to sound really, really polite, you can even add 「~でしょうか」 to the end of a 「~ます」 ending.

  • 休ませていただけますでしょうか。- May I receive the favor of resting, possibly?

Using 「でしょう」 and 「だろう」 to express strong amount of certainty (casual)


  1. 遅刻 【ち・こく】 – tardiness
  2. する (exception) – to do
  3. 時間 【じ・かん】 – time
  4. ある (u-verb) – to exist (inanimate)
  5. 言う 【い・う】 (u-verb) – to say
  6. これ – this
  7. 食べる 【た・べる】 (ru-verb) – to eat
  8. 行く 【い・く】 (u-verb) – to go
  9. 掃除 【そう・じ】 – cleaning
  10. 手伝う 【て・つだ・う】 (u-verb) – to help, to assist
  11. くれる (ru-verb) – to give
  12. そう – (things are) that way
  13. どこ – where
  14. もう – already
  15. 寝る 【ね・る】 (ru-verb) – to sleep
  16. 家 【1) うち; 2) いえ】 – 1) one’s own home; 2) house
  17. 帰る 【かえ・る】 (u-verb) – to go home

The casual equivalent of 「でしょう」 is surprisingly enough 「でしょう」. However, when you are speaking in a polite manner, the 「でしょう」 is enunciated flatly while in casual speech, it has a rising intonation and can be shortened to 「でしょ」. In addition, since people tend to be more assertive in casual situations, the casual version has a much stronger flavor often sounding more like, “See, I told you so!”

Example 1

A: Ah! We’re going to be late!

B: That’s why I told you there was no time!

Example 2

A: You’re going to eat from now aren’t you?

B: So what if I am?

Example 3

A: You’re going to help me clean, right?

B: Huh? Is that so?

「だろう」 means essentially the same thing as 「でしょう」 except that it sounds more masculine and is used mostly by males.

Example 4

A: Where is Alice?

B: Probably sleeping already.

Example 5

A: You’re going home already, right?

B: That’s right.

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