にちがいない

にちがいない Japanese Grammar Lesson

Grammar Type: Phrase

Essential Meaning: There is no doubt that

Construction: 

• (Verb / い-Adjective) informal + にちがいない
  • E.g. 話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. 高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. 静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]

Notes:

• 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. あの人ひとは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 の to convey extra confidence in the speaker’s assertion.
  • E.g. 日本にほんの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. 家いえを買かうのはあまり難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. あの人ひとは日本人にほんじんにちがいない。[That person is undoubtedly Japanese.]
  • E.g. あの人ひとは日本人にほんじんだろう。[I’m pretty sure that person is Japanese.]
  • E.g. あの人ひとは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忘わすれたにちがいない。[Shimoda-san undoubtedly forgot about today’s plans.]

あの先生せんせいの試験しけんは難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.]

二人ふたりは今頃いまごろハワイで楽たのしく泳およいでいるに違ちがいない。[Right now those two are undoubtedly having fun swimming in Hawaii.]

一人ひとりで外国がいこくへ行い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頭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:

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