Posted inN2 Grammar

Mastering に決まっている (Ni Kimatte Iru): Expressing Certainty in Japanese

Posted inN2 Grammar
Japanese Grammar Template
Meaning & Usage

✨ Basic Meaning

The basic meaning of に決まっている (ni kimatte iru) is ‘it’s certain,’ ‘it’s definite,’ ‘it’s undoubtedly,’ or ‘it’s for sure.’ It expresses the speaker’s strong conviction.

🎯 Primary Function

This grammar pattern is used to express the speaker’s strong conviction or certainty about a situation, event, or outcome. It implies that there is no doubt in the speaker’s mind, often based on logical reasoning, strong evidence, or common sense.

📋 Grammar Structure

Verb (Plain Form) + に決まっている い-Adjective (Plain Form) + に決まっている な-Adjective (Plain Form – dropping だ) + に決まっている (e.g., 静かだ → 静かに決まっている) Noun + に決まっている (e.g., 学生だ → 学生に決まっている) *Note: For Na-adjectives and Nouns, the だ after the plain form is often dropped in casual speech when followed by に決まっている, but grammatically they connect to the plain form which includes だ.*

🎭 Usage Contexts

🏢 Formal Situations

Less common in highly formal situations, as its strong, assertive tone might be perceived as too direct or subjective. In formal contexts, more objective or softened expressions might be preferred.

😊 Informal Situations

Very common in informal conversations among friends, family, or close acquaintances, where expressing strong personal opinions is natural.

✍️ Written Language

Frequently used in informal writing such as blogs, personal essays, social media posts, or casual messages to convey the writer’s firm belief.

🗣️ Spoken Language

Widely used in daily spoken Japanese. It adds emphasis to the speaker’s conviction and is a natural part of casual conversation.

💡 Common Applications

Predicting an Outcome with High Certainty
Used when the speaker is almost 100% sure about what will happen.
Example: 明日雨が降るに決まっている。(It’s definitely going to rain tomorrow.)
Stating an Obvious Truth or Conclusion
Used to convey something that is self-evident or a conclusion drawn from clear circumstances.
Example: こんなに頑張ったんだから、成功するに決まっている。(Since you worked so hard, you’re bound to succeed.)
Expressing an Unshakeable Belief
Used to convey a firm, unwavering belief or opinion.
Example: 彼がそんな嘘をつくはずがない。何かの間違いに決まっている。(He couldn’t possibly tell such a lie. It must be some kind of mistake.)
📊
Frequency
Moderately frequent in everyday spoken and informal written Japanese, particularly when expressing strong opinions or predictions.
🎚️
Difficulty
Intermediate (JLPT N2). The concept itself is straightforward, but understanding its nuances, particularly compared to similar expressions like はずだ or に違いない, is crucial for appropriate usage.
Example Sentences
毎日練習しているんだから、次の試合は彼が勝つに決まっている。
He practices every day, so he’s definitely going to win the next game.
こんなに美味しいんだから、人気が出るに決まっているよ。
It’s so delicious, so it’s bound to become popular.
彼はいつも遅刻するから、今日も遅れるに決まっている。
He’s always late, so he’ll definitely be late today too.
Notes & Nuances

📌 Important Points

Strong Personal Conviction
「に決まっている」 emphasizes the speaker’s unwavering personal belief and confidence in something, leaving no room for doubt.
Example: 彼女が嘘をつくはずがない、正直者に決まっている。(She couldn’t possibly lie, she’s definitely an honest person.)
Based on Evidence or Logic
While expressing strong conviction, it is often based on what the speaker considers clear evidence, logical reasoning, or common sense.
Example: こんなに天気がいいんだから、富士山が見えるに決まっている。(The weather is so good, Mount Fuji is definitely visible.)

⚠️ Common Mistakes

❌ Using with ambiguous or uncertain statements.
✅ Do not combine 「に決まっている」 with words that express doubt or uncertainty like 「たぶん (probably)」 or 「もしかしたら (maybe).」
「に決まっている」 implies absolute certainty, which contradicts expressions of doubt. For example, 「たぶん雨が降るに決まっている」 is incorrect.
❌ Using in overly formal or objective contexts without softening.
✅ While strong, be mindful of the assertive tone. In very formal settings, or when objectivity is required, consider softer or more neutral expressions.
Its directness might be perceived as impolite or subjective in highly formal business or academic contexts. It’s best suited for situations where personal conviction is appropriate.

🏛️ Cultural Context

Politeness Level: Generally informal to semi-formal. It carries a direct and assertive tone, so use it carefully in highly formal or polite situations where a softer expression might be more appropriate. It can sound strong or even slightly arrogant if used without considering the listener and context.
Social Situations: Most commonly used among close friends, family members, or in situations where expressing strong personal opinions is acceptable. It’s less common in interactions with superiors or strangers where more reserved language is often preferred.
Regional Variations: The basic usage is standard across Japan, though intonation and frequency of use might vary slightly by region, like with many colloquial expressions.

🔍 Subtle Differences

に決まっている vs. はずだ
「はずだ」 indicates an expectation based on reason or common sense, but still allows for a slight possibility of error or exception. 「に決まっている」 expresses a much stronger, almost undeniable conviction with virtually no room for doubt.
When to use: Use 「はずだ」 when you expect something to be true but acknowledge a small possibility of it not being so. Use 「に決まっている」 when you are absolutely convinced and want to emphasize that certainty.
に決まっている vs. に違いない
Both express strong certainty. 「に違いない」 (にちがいない) often implies certainty derived from solid evidence or logical deduction, sometimes with a more objective nuance. 「に決まっている」 can be more subjective, emphasizing the speaker’s personal unwavering belief, which might stem from intuition or strong feeling, and often feels more colloquial.
When to use: Use 「に違いない」 when your certainty is based on observable evidence or logical inference. Use 「に決まっている」 when you want to express a very strong personal conviction, often with a more casual or emphatic feel.
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📝 Conjugation Notes

「に決まっている」 consistently attaches to the plain form of verbs (辞書形, た形, ない形), い-adjectives, and the stem (without だ) of な-adjectives and nouns. Remember that for な-adjectives and nouns, the plain form technically includes だ (e.g., 静かだ, 学生だ), but the だ is often dropped before に決まっている in natural speech, making it 静かに決まっている and 学生に決まっている.

🔊 Pronunciation Tips

In casual speech, 「に決まっている」 is often pronounced more quickly, almost blending into 「にきまってる」. The small っ (sokuon) before 「ている」 indicates a glottal stop or a brief pause, adding to the emphatic feel. Pay attention to the rising intonation at the end when asking a rhetorical question with this pattern (e.g., 「〜に決まっているの？」).

🧠 Memory Tips

Think of 「決まる (kimaru)」 meaning “to be decided” or “to be fixed.” So, 「に決まっている」 literally means “it is decided/fixed to be…” or “it is set that it is/will be…” This helps reinforce the idea of certainty and no room for change.

Vocabulary List
決まる
kimaru
to be decided; to be fixed
間違い
machigai
mistake; error
練習
renshuu
practice
試合
shiai
game; match
勝つ
katsu
to win
美味しい
oishii
delicious; tasty
人気が出る
to become popular
Kanji List
決
ケツ, き.める, き.まる
decide, fix
間
カン, ケン, あいだ, ま
interval, space
違
イ, ちが.う, ちが.える
difference, deviate
練
レン, ね.る
practice, train
習
シュウ, ジュ, なら.う
learn, custom
試
シ, こころ.みる, ため.す
test, try
合
ゴウ, ガッ, カッ, あ.う
fit, join, meet
勝
ショウ, か.つ, まさ.る
win, prevail
美
ビ, ミ, うつく.しい
beauty, beautiful
味
ミ, あじ, あじ.わう
flavor, taste
人
ジン, ニン, ひと
person
Practice Exercises
彼は一日中ゲームばかりしているから、___に決まっている。
A) 試験に合格する
B) 試験に失敗する
C) 試験を受ける
D) 試験を休む
この店はいつも行列ができている。____に決まっている。
A) まずい
B) 空いている
C) おいしい
D) 高い
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