Wild Nihongo!


にちがいない Japanese Grammar Lesson

Grammar Type: Phrase

Essential Meaning: There is no doubt that


  • (Verb / い-Adjective) informal + にちがいない
    • E.g. はなすにちがいない [There’s no doubt that X talked / There’s no doubt that X will talk]
    • E.g. たかいにちがいない [There’s no doubt that X is expensive]
  • (な-Adjective Stem / Noun) + [X / だった] + にちがいない
    • E.g. しずかにちがいない [There’s no doubt that X is quiet]
    • E.g. 先生せんせいだったにちがいない [There’s no doubt that X was a teacher]


  • にちがいない conveys a strong sense of probability / confidence in some proposition. In other words, the speaker believes that the proposition that precedes にちがいない is undoubtedly true or correct.
    • E.g. あのひと日本人にほんじんにちがいない。[That person is undoubtedly Japanese.]
  • In written Japanese, the proposition that precedes にちがいない may be nominalized with to convey extra confidence in the speaker’s assertion.
    • E.g. 日本にほん経済けいざいはよくなったのにちがいない。[There’s no doubt about the fact the Japan’s economy has greatly improved.]
    • E.g. いえうのはあまりむずかしくないのにちがいない。[There’s no doubt that buying a house is not so difficult.]
  • In terms of confidence: にちがいない > だろう > かもしれない. In other words, にちがいない conveys the most confidence, and かもしれない conveys a low level of confidence.
    • E.g. あのひと日本人にほんじんにちがいない。[That person is undoubtedly Japanese.]
    • E.g. あのひと日本人にほんじんだろう。[I’m pretty sure that person is Japanese.]
    • E.g. あのひと日本人にほんじんかもしれない。[That person is perhaps Japanese.]
  • There are cases in which にちがいない can be interchanged with はずだ. The difference between the two is that はずだ expresses an expectation based on reliable facts or evidence, while にちがいない is not necessarily evidence-based.
    • E.g. そのアパートはきれいなはずだ。[I expect that apartment is clean.] The implication here is that the speaker’s expectation is based on some kind of evidence. Perhaps the apartment owner is a very tidy person, so it’s reasonable to expect that their apartment would be clean.
    • E.g. そのアパートはきれいにちがいない。[That apartment is undoubtedly clean.] The speaker is very confident in his or her assertion that the apartment is clean, but this confidence may or may not be justified.

Example Sentences:

下田しもださんは今日きょうのことをわすれたにちがいない。[Shimoda-san undoubtedly forgot about today’s plans.]

あの先生せんせい試験しけんむずかしいにちがいない。[That teacher’s tests are undoubtedly difficult.]

ベイリーさんはテニスが上手じょうずにちがいない。[There is no doubt that Ms. Bailey is good at tennis.]

二人ふたり今頃いまごろハワイでたのしくおよいでいるにちがいない。[Right now those two are undoubtedly having fun swimming in Hawaii.]

一人ひとり外国がいこくくのは大変たいへんにちがいない。[There is no doubt that going abroad on one’s own is difficult.]

山口やまぐちさんはあたまがいいにちがいない。[Mr. Yamaguchi is undoubtedly smart.]

あれはトンプソンさんにちがいない。[There is no doubt that is Mr. Thompson.]

WILD Examples:

Listen to this line from 1:25: 今夜こんや月夜つきよにちがいない [Tonight will certainly be a moonlit night]

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