ことにする means to decide to. It is a JLPT N4 Japanese grammar pattern used to say that the speaker decides to do something.
This grammar point often appears in conversation, written explanations, formal notices, and JLPT-style reading questions. If you want to say that the speaker decides to do something, ことにする is a useful pattern to learn after the N5 basics.
What does ことにする mean?
Use ことにする when you want to say that the speaker decides to do something.
Natural translations include:
- to decide to
- to decide to
- to decide to
The exact English translation changes with context. Focus on what the grammar point does in the sentence first, then choose the English phrase that sounds natural.
How to form ことにする
Verb dictionary/ない form + ことにする
Examples of the pattern:
- 行くことにする
- 買わないことにする
- 勉強することにする
Pay attention to the word form before the pattern. Many JLPT N4 mistakes happen because the meaning is understood, but the grammar is attached to the wrong form.
When is ことにする used?
Use ことにする in situations like:
- explaining a condition, reason, decision, or time relationship
- making a sentence more specific than a basic N5 pattern
- understanding natural Japanese in conversation or reading
Tone and register:
- neutral unless the grammar itself is marked as casual, humble, honorific, or formal
- Common in daily speech, textbook examples, and JLPT N4 reading questions
ことにする example sentences
- 毎日日本語を勉強することにしました。 — I decided to study Japanese every day.
- 今日は早く寝ることにします。 — I will decide to sleep early today.
- 新しいパソコンは買わないことにしました。 — I decided not to buy a new computer.
- 週末に友達と会うことにしました。 — I decided to meet my friend on the weekend.
- バスではなく電車で行くことにします。 — I will decide to go by train, not bus.
Read the Japanese sentence first, then check the English translation. Try to notice what the grammar point contributes: condition, timing, limitation, possibility, decision, politeness, or emphasis.
Nuance of ことにする
The key nuance is focuses on the speaker’s own decision.
This matters because ことにする may look simple in English, but the Japanese form tells you whether the speaker is describing a time, a condition, a decision, a possibility, or a social relationship.
For example:
- In context, ことにする helps make the sentence more precise than a direct English translation.
- Compared with ことになる, it has a different focus even when both patterns appear in similar sentences.
ことにする vs ことになる
Both {jp} and {similar} can appear in related sentences, but they are different.
ことにする:
- is the target JLPT N4 pattern in this lesson
- carries the specific nuance explained above
ことになる:
- is useful for comparison because learners often mix it up
- may use a different form, tone, or sentence focus
Quick contrast examples:
- Target pattern: 毎日日本語を勉強することにしました。 — I decided to study Japanese every day.
- Related pattern with ことになる: compare the form and ask whether the sentence is about timing, condition, ability, decision, or politeness.
If you are unsure which one to use, identify the main job of the sentence before translating it into English.
Common mistakes with ことにする
Watch out for these mistakes:
- Using it with the wrong verb, noun, or adjective form
- Confusing it with ことになる because the English translation can look similar
- Translating it too literally instead of reading the whole sentence context
A good study habit is to write one short sentence and then change only the grammar point. This makes the difference between similar patterns easier to feel.
Is ことにする on the JLPT?
Yes. ことにする is commonly taught as JLPT N4 grammar.
That means learners should be able to:
- recognize it in reading
- understand its nuance in context
- use it in simple original sentences
For test preparation, do not only memorize the English gloss. Practice identifying the words around the grammar point, because JLPT questions often test structure and context together.
Practice questions for ことにする
Try making your own sentences with these prompts:
- Write one sentence using the basic pattern.
- Change the sentence into polite or casual style if possible.
- Compare it with the related pattern from the comparison section.
Keep the sentences short at first. Once the form feels natural, add time words, places, reasons, or contrast to make the sentence more realistic.
Learn ことにする with Kanjiru
If you want to review ことにする together with kanji, vocabulary, and other JLPT N4 patterns, Kanjiru helps you practice Japanese in short, focused sessions.
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