Koto Expressions in Japanese

Overview

The word こと (thing, matter, fact) is one of the most versatile grammatical elements in Japanese. While you may have first encountered it as a nominalizer (turning verbs into noun phrases) or in the pattern ことができる (to be able to), at the B2 level こと appears in a range of advanced expressions that convey decisions, outcomes, necessity, and advice. Mastering these patterns is a major step toward natural, sophisticated Japanese.

At its core, こと abstracts an action into a concept — "the act of doing X" or "the matter of X." This abstraction then combines with verbs like する (to do), なる (to become), and ある (to exist) to create expressions with precise and distinct meanings. For instance, ことにする means "to decide to," while ことになる means "it has been decided that" — a subtle but crucial difference in agency that reflects Japanese communication norms.

These expressions are pervasive in everyday Japanese — announcing personal decisions, reporting workplace changes, reassuring someone there is no need to worry, and giving life advice. Understanding them will unlock a significant portion of intermediate-to-advanced conversation and reading material.

Formation / How It Works

Pattern 1: ことにする — "Decide To"

The speaker actively makes a decision. Emphasizes personal agency.

Formation	Example	Meaning
dictionary form + ことにする	行くことにする	decide to go
ない form + ことにする	食べないことにする	decide not to eat
past: ことにした	留学することにした	decided to study abroad

Pattern 2: ことになる — "It Has Been Decided / It Turns Out"

The outcome is presented as resulting from circumstances, not personal will. Common for workplace announcements and life changes.

Formation	Example	Meaning
dictionary form + ことになる	転勤することになる	it's been decided that I'll transfer
ない form + ことになる	行かないことになった	it's been decided that I won't go
past: ことになった	東京で働くことになった	it turned out I'll work in Tokyo

Pattern 3: ことはない — "No Need To / There Is No..."

Expresses that something is unnecessary or that a situation does not exist.

Formation	Example	Meaning
dictionary form + ことはない	心配することはない	there's no need to worry
dictionary form + ことはない	急ぐことはない	there's no need to hurry

Pattern 4: ことだ — "Should / The Key Is To"

Gives advice or states what is important. Authoritative, sometimes preachy tone.

Formation	Example	Meaning
dictionary form + ことだ	よく寝ることだ	the key is to sleep well
ない form + ことだ	無理しないことだ	the important thing is not to overdo it

Pattern 5: ことがある — "There Are Times When / Have Experienced"

Formation	Example	Meaning
dictionary form + ことがある	忘れることがある	sometimes I forget
た-form + ことがある	行ったことがある	have been (experienced)

Summary Table

Pattern	Structure	Agency	Meaning
ことにする	dict. + ことにする	Speaker decides	I decided to...
ことになる	dict. + ことになる	External/circumstantial	It's been decided that...
ことはない	dict. + ことはない	—	No need to...
ことだ	dict. + ことだ	—	Should / the key is...
ことがある	dict./た + ことがある	—	Sometimes / have experienced

Examples in Context

Japanese	English	Note
来年、留学することにしました。	I've decided to study abroad next year.	Personal decision (past)
来月から東京で働くことになりました。	Starting next month, I'll be working in Tokyo.	External decision/outcome
心配することはありません。	There's no need to worry.	Reassurance (polite form)
健康でいるには、よく寝ることだ。	To stay healthy, the key is to sleep well.	Advice
毎朝ジョギングすることにしています。	I make a point of jogging every morning.	Habitual decision (している)
会議は来週に延期することになりました。	It's been decided that the meeting will be postponed to next week.	Workplace announcement
そんなに急ぐことはないですよ。	There's no need to hurry that much.	Calming someone down
成功するには、あきらめないことだ。	To succeed, the key is not to give up.	Life advice
日本に行ったことがありますか？	Have you ever been to Japan?	Experience question
たまに夜遅くまで起きていることがあります。	Sometimes I stay up late at night.	Occasional occurrence
お酒を飲まないことにしています。	I've made a point of not drinking alcohol.	Ongoing personal policy
転職することになって、引っ越します。	It's turned out that I'm changing jobs, so I'll move.	Life change announcement

Common Mistakes

Wrong: 東京で働くことにしました。(when the company decided, not you) Right: 東京で働くことになりました。 Why: ことにする implies the speaker made the decision. ことになる presents the outcome as determined by external circumstances (the company, fate, etc.). In Japanese, people often use ことになる even for personal decisions to sound humble or to avoid appearing forceful.

Wrong: 心配するのことはない。 Right: 心配することはない。 Why: In this pattern, こと directly follows the plain verb form. Do not insert の before こと — the structure is verb + ことはない.

Wrong: 寝ることです。(intending advice) Right: 寝ることだ。 Why: While ことです is grammatically possible in polite speech, the advice pattern ことだ is most naturally expressed with the plain copula だ. Using です can sound overly polite or unnatural for this particular expression.

Wrong: 留学するのことにしました。 Right: 留学することにしました。 Why: Do not add の between the verb and こと in these fixed expressions. The verb connects directly to こと.

Wrong: 食べることにならない。(intending "I decided not to eat") Right: 食べないことにした。 Why: To express deciding NOT to do something, negate the verb before こと: ない form + ことにする. Do not negate なる — that would change the meaning entirely.

Usage Notes

The distinction between ことにする and ことになる is deeply tied to Japanese communication culture. Japanese speakers often prefer ことになる even when they themselves made the decision, because it deflects personal responsibility and sounds more modest. In business settings, ことになりました is the standard way to announce transfers, schedule changes, and policy decisions — even if the speaker was the one who decided.

ことにしている (habitual form of ことにする) expresses a personal rule or policy that you maintain: 毎日運動することにしています (I make it a rule to exercise every day). This is distinct from the one-time decision ことにした.

ことだ (advice) carries an authoritative tone similar to ものだ. It is often used by older speakers, in self-help writing, and in proverbs. Be mindful that using it too freely in conversation can sound preachy.

ことはない can also be used emphatically to mean "it's not the case that...": 全く知らないということはない (It's not the case that I don't know at all). This overlaps with the わけではない pattern.

Practice Tips

• Practice ことにする for daily decisions. Each time you make a small decision, verbalize it: 今日は早く寝ることにする (I've decided to go to bed early today). This builds the habit of expressing agency through this pattern.
• Listen for ことになる in news and announcements. Japanese news broadcasts, workplace emails, and official statements frequently use ことになりました. Paying attention to these real-world examples will solidify your understanding of the "external decision" nuance.
• Pair ことはない with reassurance. When a friend is worried, practice responding with this pattern: 心配することはないよ, 急ぐことはないよ. This is a practical, empathetic use that comes up regularly in conversation.

Related Concepts

• Ability ことができる
• Advanced Nominalization