N2Possibility & Probability

Plain form + に決まっている / N・Na-adj (no だ) + に決まっている

Q: Is "Using in formal writing" correct?

No. The correct form is "Avoid using in formal writing". This pattern is more conversational and less formal than other expressions of certainty, so it's best to avoid using it in formal writing or in situations where you want to convey a more objective tone.

Q: Is "Confusing with ～に違いない" correct?

No. The correct form is "Use ～に違いない for more objective evidence". ～に違いない is based more on objective evidence, so use it when you have clear evidence to support your claim. Use に決まっている when you're expressing a strong, subjective belief.

Q: Is "Adding 'だ' before the pattern for Nouns/Na-adjectives" correct?

No. The correct form is "Don't add 'だ' before the pattern for Nouns/Na-adjectives". When using this pattern with Nouns or Na-adjectives, don't add 'だ' before the pattern. Instead, use the plain form of the verb or the Noun/Na-adjective directly followed by に決まっている.

Definitely; bound to

Definition

Meaning

The grammar pattern "Plain form + に決まっている / N・Na-adj (no だ) + に決まっている" is used to express a very strong, often subjective, belief that something is obviously true. It implies a high degree of certainty and conviction, but the evidence for this conviction may not be entirely objective. This pattern is more conversational and less formal than other expressions of certainty, such as ～に違いない, which is based more on objective evidence. The use of this pattern can come across as more assertive and persuasive, but also potentially more subjective and open to debate.

Structure

Formation Rules

Form	Pattern	Example
Plain form of verb	Verb + に決まっている	見る + に決まっている = 見るに決まっている
Plain form of verb	N・Na-adj + に決まっている	彼 + に決まっている = 彼に決まっている
Plain form of verb	N・Na-adj (no だ) + に決まっている	彼は + に決まっている = 彼はに決まっている

Examples

Example Sentences

そんなの、嘘に決まっている。信じちゃだめだよ。

Sonna no, uso ni kimatte iru. Shinjichanda me da yo.

That's definitely a lie. Don't believe it.

そんなの (that's definitely) + 嘘に決まっている (it's a lie) + 信じちゃだめ (don't believe it)

練習しないで試合に出たって、負けるに決まっている。

Renshu shinai de shiai ni deta tte, makenu ni kimatte iru.

If you don't practice, you'll definitely lose in the game.

練習しないで (don't practice) + 試合に出たって (you'll be in the game) + 負けるに決まっている (you'll definitely lose)

一人でそんな重い荷物を持てるに決まっている。

Hitori de sonna omoi nimotsu o motseru ni kimatte iru.

It's definitely impossible for one person to carry such a heavy load.

一人で (one person) + そんな重い荷物を持てる (can carry such a heavy load) + に決まっている (it's definitely impossible)

Context

Usage Notes

This pattern is more conversational and less formal than other expressions of certainty. It's often used in informal settings, such as with friends or in casual conversations. Be careful not to confuse it with ～に違いない, which is based more on objective evidence. Also, be aware that the use of this pattern can come across as more assertive and persuasive, but also potentially more subjective and open to debate.

Watch out

Common Mistakes

Using in formal writing

Avoid using in formal writing

This pattern is more conversational and less formal than other expressions of certainty, so it's best to avoid using it in formal writing or in situations where you want to convey a more objective tone.

Confusing with ～に違いない

Use ～に違いない for more objective evidence

～に違いない is based more on objective evidence, so use it when you have clear evidence to support your claim. Use に決まっている when you're expressing a strong, subjective belief.

Adding 'だ' before the pattern for Nouns/Na-adjectives

Don't add 'だ' before the pattern for Nouns/Na-adjectives

When using this pattern with Nouns or Na-adjectives, don't add 'だ' before the pattern. Instead, use the plain form of the verb or the Noun/Na-adjective directly followed by に決まっている.

Strategy

JLPT Exam Tips

When using this pattern in the JLPT exam, be careful to use it correctly in context. Make sure to choose the correct verb form and to use the pattern in a way that's consistent with the tone and style of the sentence.

In context