Tomodai
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ことにする

To decide to do / to make it a rule that → expresses a decision made by the speaker (or subject)

N1

Meaning

To decide to do / to make it a rule that → expresses a decision made by the speaker (or subject)

Formation

Verb (dictionary form) + ことにする
Verb (ない-form) + ことにする

Explanation

ことにする is used when someone actively makes a decision.

🔸 ことにする = decision by will

Key idea:
👉 “After thinking about it, I decide to do this.”

Important nuances:

  • The decision is intentional

  • The subject has control and choice

  • Often reflects personal will or policy

  • Can be used for:

    • one-time decisions

    • habitual rules (“I’ve decided to always…”)

It is commonly used in:

  • personal statements

  • explanations of policy or plans

  • written and spoken Japanese

  • JLPT N2–N1 contexts