ことにする
- 1To decide to do something by one's own deliberate choice.Ex. 1
- 2In the negative form, to decide not to do something, or to decide to stop doing it.Ex. 2
This browser can't play pronunciations (needs Safari 18.4 or later, or Chrome / Edge / Firefox).
Neutral in register and common in both conversation and writing. It is used to report choices such as lifestyle changes. It can also report the decisions of others or organizations (e.g. 会社は在宅勤務を認めることにした). ことにしました is typical when telling someone about a decision, and ことにします when announcing it on the spot. It foregrounds a deciding agent, unlike ことになる, which presents the matter as a settled outcome.
Learners sometimes use ことにする where no deciding agent is presented; ことになる suits outcomes presented as arranged by circumstances.
Note that ことにしました means the decision was made, not that the action itself has already been done.
Do not attach ことにする directly to a noun; put a verb form before こと.
- ことになるN4「ことになる」indicates a decision formed by others, an organization, or circumstances, with an objective and tactful tone; when reporting your own decision, 「ことになりました」is also commonly used to show modesty. It also has a calculation sense of "the result comes to…".
- 〜ことにしているN3「〜ことにしている」focuses on the continuing state after the decision, expressing a habit or principle you have kept up, or a plan still in effect; 「ことにした」only states that a decision has been made. For long-term habits or self-imposed rules, use 「〜ことにしている」.
- つもりN5「つもり」expresses an intention or plan, while 「ことにする」emphasizes the act of making a decision; 「つもりだった」often implies it wasn't realized. With the た形, 「つもり」usually means subjectively "assuming (mistakenly)", while 「ことにする」means deliberately "treating it as".
- ようにするN4「ようにする」means making a conscious effort to do (or not do) something, or trying to bring about a certain state; 「ことにする」centers on making a decision and also has the "treat it as" sense. For habits, 「ことにしている」is a rule you've set, while 「ようにしている」is trying to keep it up.
- 予定だN4「予定だ」states an already-arranged schedule, often paired with a specific time, and doesn't highlight who made the decision; 「ことにする」emphasizes the subject's active decision. 「予定だ」can attach after 「名詞＋の」, and 「予定だった」can indicate that the original plan changed or wasn't realized.
ことにする foregrounds a subject's deliberate decision, while ことになる presents the matter as a settled outcome without highlighting who decided, and 〜ことにしている describes an ongoing habit or rule that follows from such a decision. つもり expresses an intention and 予定だ a scheduled plan, neither of which stresses the act of deciding, while ようにする means making an effort so that something happens.
