N4 Purpose & Change

~になる/ことになる: meaning, usage and examples

~になる/ことになる means: ~になる: to become; ~ことになる: it has been decided that...

Updated 9 November 2026 · By the My Senpai team · Spotted a mistake? Tell us

Examples

1. 来月らいげつ、東京とうきょうに転勤てんきんすることになりました。

   It has been decided that I will transfer to Tokyo next month.

2. 今年ことしから新あたらしい制度せいどになります。

   A new system will be implemented from this year.

3. 来年らいねんの春はる、結婚けっこんすることになりました。

   It has been decided that I will get married next spring.

4. この学校がっこうでは、教室きょうしつでくつをぬぐことになっています。

   At this school, the rule is to take off your shoes in the classroom.

When to use it

になる means "to become": 先生せんせいになる, 静しずかになる, 高たかくなる. ことになる means "it has been decided that", when the decision was made by someone else or came from circumstances: 来月らいげつ、大阪おおさかに転勤てんきんすることになりました. ことになっている describes a rule, custom or arrangement that is already fixed and that people are expected to follow: この学校がっこうでは、くつをぬぐことになっています.

Nuance

ことになりました is polite and modest even when the speaker made the choice, because it presents the result as an outcome rather than a personal decision. It is common in announcements of transfers, marriages and schedule changes.

Compare

ことになる vs ことにする: ことにする is the speaker's own decision (行いくことにしました: I decided to go); ことになる is decided by others or by the situation (行いくことになりました: it was decided that I go). ことになる vs ようになる: ようになる is a gradual change in ability or habit, not a decision.

Tip: Think "なる = it became, someone or something else decided" and "する = I did it, I decided". The same pair appears in にする and になる.