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JLPT N4Grammar Patterns

ことにする— Decide to / Make it a rule to

Expresses a personal decision made by the speaker — an active, deliberate choice by the subject, in contrast to ことになる (a decision by external forces).

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Pro lessonUNIT 30 · GRAMMAR PATTERNS

Structure · 形

[Verb dictionary / plain negative] + ことにする / した

Examples · 例文

  • 毎朝ジョギングすることにしました。

    Maiasa jogingu suru koto ni shimashita.

    I decided to go jogging every morning.

    Personal decision → ことにした

  • お酒を飲まないことにした。

    Osake wo nomanai koto ni shita.

    I decided not to drink alcohol.

    飲まない (negative) + ことにした = decided NOT to

  • 毎日日本語を勉強することにしている。

    Mainichi nihongo wo benkyou suru koto ni shite iru.

    I make it a rule to study Japanese every day.

    ことにしている = have made it a standing habit/rule

Usage notes · 注意

  • ことにする (personal decision) vs ことになる (external / natural outcome).
  • ことにしている = an ongoing habit or rule you've set for yourself.
  • Contrast: 来年日本に行くことにした (I decided to go) vs 来年日本に行くことになった (it was decided I'll go — external).

Commonly confused with

The JLPT rarely asks whether you recognise a pattern — it asks which of several similar patterns fits. These are the ones ことにする is tested against.

vsことになる

ことにする = you actively choose; ことになる = the decision is framed as made by others/circumstances.

vsことにしている

The 〜ている form marks a continuing self-imposed habit/policy; ことにした marks the single moment you decided.

vsつもり (intend to)

つもり states an intention/plan that may still change; ことにする marks a decision already firmly made.

More grammar patterns

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