N2 Assertion, Likelihood, and Norms

~に相違そういない: meaning, usage and examples

~に相違そういない means: no doubt... / must be...

Updated 9 November 2026 · By the My Senpai team · Spotted a mistake? Tell us

Examples

1. 彼かれが犯人はんにんに相違そういない。

   He must be the culprit, no doubt.

2. この計画けいかくは成功せいこうするに相違そういない。

   This plan will no doubt succeed.

3. この手紙てがみの字じは、田中たなかさんが書かいたものに相違そういない。

   The handwriting in this letter is undoubtedly Mr. Tanaka's.

4. この絵えは有名ゆうめいな画家がかの作品さくひんに相違そういない。

   This painting is undoubtedly the work of a famous artist.

When to use it

Use に相違そういない to state a conclusion the speaker is very sure of, based on evidence or reasoning. It means "there is no doubt that..." and usually follows a clue such as handwriting, style or traces, as in この絵えは有名ゆうめいな画家がかの作品さくひんに相違そういない (this painting is undoubtedly the work of a famous artist).

Nuance

Formal and written; found in novels, reports and formal speech. In conversation it sounds stiff. It expresses strong certainty based on reasoning, but it is still the speaker's judgment, not a proven fact.

Compare

に違ちがいない has the same meaning but is used in everyday speech: 田中たなかさんは疲つかれているに違ちがいない. に相違そういない is its formal written version. はずだ is based on logic or known facts: 荷物にもつは今日きょう届とどくはずだ. にほかならない defines something rather than guessing.

Tip: に相違そういない = written に違ちがいない. On the test they are interchangeable in meaning; pick 相違そうい for formal text.