Posted inN2 Grammar

Mastering 「に相違ない (ni soui nai)」: Expressing Absolute Certainty in Japanese (JLPT N2 Grammar)

Posted inN2 Grammar
Japanese Grammar Template
Meaning & Usage

✨ Basic Meaning

「に相違ない」means “there is no mistake that…”, “it is certain that…”, or “it must be that…”. It expresses a very high degree of conviction or certainty about a fact or inference.

🎯 Primary Function

Its primary function is to assert a strong, almost absolute conviction or a logical conclusion based on evidence, facts, or strong reasoning. It conveys a sense of undeniable truth.

📋 Grammar Structure

「に相違ない」attaches to the plain form of verbs and い-adjectives. For な-adjectives and nouns, it typically attaches after 「である」, though sometimes directly to a noun in very formal or concise writing, especially in headlines.

🎭 Usage Contexts

🏢 Formal Situations

Highly common and appropriate in formal settings, discussions, and declarations.

😊 Informal Situations

Rarely used in informal conversation due to its formality; it would sound overly stiff or even pompous.

✍️ Written Language

Very common in formal written Japanese, such as academic papers, legal documents, official reports, news articles, and business correspondence.

🗣️ Spoken Language

Less common in everyday spoken Japanese. When used, it is typically in formal speeches, presentations, or situations where a strong, definitive statement is required.

💡 Common Applications

Stating conclusions from evidence
Used to present a conclusion drawn from clear and undeniable facts or evidence, emphasizing that there can be no other interpretation.
Example: 彼の無罪は、提出された証拠から考えても、真実に相違ない。 (His innocence, considering the evidence presented, must certainly be true.)
Making strong assertions
For making a very firm assertion or declaration that leaves little to no room for doubt.
Example: この改革が経済に良い影響を与えることに相違ない。(There is no doubt that these reforms will have a positive impact on the economy.)
Expressing strong logical inference
When inferring something with a very high degree of probability based on logical reasoning or a set of circumstances.
Example: これだけの準備をしたのだから、成功するに相違ない。(Since we’ve prepared this much, we are sure to succeed.)
📊
Frequency
Moderate to high in formal and written contexts; low in casual spoken contexts.
🎚️
Difficulty
N2
Example Sentences
彼の証言は真実に相違ない。
His testimony must certainly be true.
この問題の解決は容易ではないに相違ない。
Solving this problem will certainly not be easy.
彼はきっと犯人に相違ない。
He must certainly be the culprit.
Notes & Nuances

📌 Important Points

High Degree of Certainty
「に相違ない」 expresses an extremely high degree of certainty, bordering on absolute truth. It is stronger and more definitive than 「に違いない」.
Example: 彼の言葉は嘘に相違ない。 (His words are undoubtedly a lie.) – Very strong conviction.
Formal and Objective Tone
It often carries an objective and formal tone, suggesting that the conclusion is based on undeniable facts or logical deduction rather than personal opinion.
Example: 統計を見る限り、景気は回復傾向にあるに相違ない。 (As far as the statistics show, the economy is undoubtedly on a recovery trend.)

⚠️ Common Mistakes

❌ Using in casual conversations
✅ Use 「に違いない」, 「はずだ」, or more casual expressions like 「～でしょう」 or 「～に決まっている」 instead.
「に相違ない」 sounds overly formal and stiff in casual settings, making the speaker sound unnatural or even arrogant.
❌ Using without sufficient evidence
✅ Ensure there is concrete evidence or very strong logical reasoning to support the statement when using 「に相違ない」.
Because it expresses such a high level of certainty, using it without strong backing can make your statement seem unfounded or overly assertive.

🏛️ Cultural Context

Politeness Level: High. It conveys a sense of professionalism and formality.
Social Situations: Primarily used in formal or academic discourse, official statements, and written communication where precision and strong assertion are required.
Regional Variations: Generally consistent across regions as it is a formal grammatical pattern.

🔍 Subtle Differences

に相違ない vs. に違いない
「に相違ない」 is more formal and conveys a stronger, almost absolute certainty, often used in written or highly formal contexts. 「に違いない」 is also strong certainty but is more commonly used in both written and spoken Japanese, and can sometimes imply a strong personal conviction.
When to use: Use 「に相違ない」 when you need to express an undeniable truth or conclusion in a formal setting. Use 「に違いない」 when expressing strong conviction that is still suitable for broader contexts, including spoken.
に相違ない vs. はずだ
「に相違ない」 signifies a near-absolute certainty based on evidence or logical conclusion. 「はずだ」 indicates an expectation based on reasoning, common sense, or prior information, but still leaves a small margin for error.
When to use: Use 「に相違ない」 for very firm, undeniable conclusions. Use 「はずだ」 when expressing something that is “supposed to be” or “expected to be” based on logical grounds.
に相違ない vs. だろう
「だろう」 (or でしょう) is a conjecture or probability, indicating a guess or likelihood with a much lower degree of certainty than 「に相違ない」.
When to use: Do not confuse these. 「に相違ない」 is for certainty, 「だろう」 is for probability or speculation.

📝 Conjugation Notes

Verbs and い-adjectives directly take the plain form + に相違ない. な-adjectives and Nouns typically take the である form + に相違ない (e.g., 静かであるに相違ない, 学生であるに相違ない). In very formal or condensed writing, nouns can sometimes directly precede に相違ない (e.g., 真実に相違ない).

🔊 Pronunciation Tips

The pronunciation is 「に・そう・い・ない」. The “そう” part should be clear, and the overall phrase flows smoothly. There’s no specific difficult pronunciation point, but maintaining a natural, authoritative tone when speaking it matches its formal usage.

🧠 Memory Tips

Break it down: 「相違 (そうい)」 means “difference” or “mistake”. So, 「相違ない (そういない)」 literally means “there is no mistake/difference”. This helps to remember its meaning of “undoubtedly” or “certainly”. Think of it as “without fail.”

Vocabulary List
相違
soui
difference, mistake
証言
shougen
testimony
真実
shinjitsu
truth
解決
kaiketsu
solution, settlement
容易
youi
easy, simple
犯人
hannin
culprit, criminal
成功
success
Kanji List
相
そう
mutual, reciprocal
違
い
differ, contradict
証
しょう
evidence, proof
言
げん
word, speech
真
しん
true, reality
実
じつ
truth, reality
解
かい
unravel, solve
決
けつ
decide, determine
容
よう
form, container
易
い
easy
犯
はん
crime, offend
Practice Exercises
彼は間違いなくその件の専門家＿＿＿＿。
a) であるはずだ
b) であるに相違ない
c) だろう
d) かもしれない
この状況から見て、計画は変更される＿＿＿＿。
a) 違いがある
b) に相違ない
c) そうだ
d) らしい
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