Grammar Info

N3 Lesson 3: 8/22


To decide on, Have decided to


Verb[る]+ ことにする
Verb[ない]+ ことにする


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About ことにする

In a similar way to how にする means to 'decide on' something, ことにする means to decide on a situation, or course of action. This grammar point is a combination of (こと) 'thing' in its role as a nominalizer (a word that creates a noun-phrase), and にする 'to make it (A)'. Literally this grammar structure can be translated as 'to do (A)', or 'to make it (A)'.
ことにする may be used with verb-phrases that are either in the affirmative, or negative (using ない) forms. As こと itself is a noun, the verb (or auxiliary verb) that comes before it will need to be in its attributive form.
  • 今日(きょう)はワクチン()ったから明日(あした)仕事(しごと)(やす)ことにする
    Today I got vaccinated, so I will go with taking the day off tomorrow.
  • タマキさん箱根(はこね)()ことにする
    I have decided to go to Hakone with Tamaki-san.
  • 今日(きょう)(あめ)()ているから明日(あした)()ことにしない
    It is raining today, don't you want to make it that we go tomorrow?
  • 勝手(かって)(ぼく)()くという(こと)にしないでください
    Please don't decide that I will go without asking me. (Please don't assume that I want to go)
にする is a strong expression, which tends to make the speaker sound like they are fairly resolute in their decision.
The する in にする itself may also be seen using ない, to mean that someone has decided 'against' doing something. Due to this, careful attention will need to be paid to the overall structure of the sentence.
  • これから(にく)()べることにする
    I have decided to eat meat from now on.
  • これから(にく)()べることにしない
    Let's decide to eat meat from now on.
  • これから(にく)()べないことにする
    I have decided to not eat meat from now on.
  • これから(にく)()べないことにしない
    I have decided to not not eat meat from now on.




    Since today is April Fool's, I've decided to only tell lies.


    We've decided to take the commemorative photo at that place.


    I didn't know if it would finish at nine but, I decided to go home in advance.


    I have decided not to say anything else. If I say something, it would piss her off.


    I have decided to hand out this product for free.

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ことにする – Grammar Discussion

Most Recent Replies (9 in total)

  • Chrispy


    Any update when this grammar point will be added? It should be N2/N1 (according to the Try N2 book or JLPT Sensei).

  • clover1


    I’ve run into some sources which say (example) that ことにしている means “do something as a regular practice,” while ことにする or ことにした is “decide(d) to do.”

    I’m curious about how the difference in tenses play out in this example:

  • Meatdog


    The difference between ことにする and ことになる?

    Looking at the examples, is it true that 事ことにする would be used for someone specific, like me,they,her,she,them for example? And ことになる would be used for some indirect unmentioned person or thing that did the deciding?

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