〜に決まってる

It must be...; It’s obvious that...

1. Translation

"〜に決まってる" is used to express certainty or a strong assumption about something, often with a tone of "it's obvious" or "of course."

2. Overview

This phrase is used when the speaker is certain about a particular fact or when something is very obvious. It adds emphasis to the speaker's confidence or judgment.

3. Structure

• Grammar Structure:

  • Noun + に決まってる
  • Verb (plain form) + に決まってる
  • い-adjective + に決まってる
  • な-adjective + に決まってる

• Explanation: The phrase attaches to nouns, verbs, or adjectives and emphasizes that something is certainly or obviously true.

4. Usage Explanation

• Connection:

  • This structure is commonly used in spoken language to strongly assert an opinion or conclusion.

• Translation: It translates to "It must be...", "Of course...", or "It's obvious that..."

5. Example Sentences

1. 彼が犯人に決まってる。
   He must be the culprit.

2. そんな話、嘘に決まってるよ。
   That story must be a lie.

3. 彼女は喜ぶに決まってる。
   She’ll definitely be happy.

4. この試験は難しいに決まってる。
   This test is bound to be difficult.

5. 彼が勝つに決まってる。
   He’s sure to win.

6. Alternative Grammar

• 〜はずだ: Also expresses certainty, but with a slightly softer tone.
  • Example: 彼が犯人のはずだ。
    He should be the culprit.

7. Related Grammar

• 〜に違いない: Similar in meaning, it also expresses strong belief or assumption.
  • Example: 彼が犯人に違いない。
    He must be the culprit.

8. Notes

• Context: "〜に決まってる" is more casual and often used in speech when expressing a strong opinion or certainty.

• Tone: It has a strong, emphatic tone, so it might feel direct or forceful in some situations.

9. Summary

"〜に決まってる" is a phrase used to express strong certainty or obviousness, commonly used in informal speech to emphasize what the speaker believes to be clearly true.