～こと (nominalizer)

Japanese Grammar Basic Japanese ★★★★★ 5/5 neutral ことkoto
読み こと
ローマ字 koto
形 Verb (plain form) + こと / い-Adj + こと / な-Adj + な + こと

意味

A nominalizer that converts a verb phrase or clause into a noun phrase. It indicates a relatively objective or emotionally detached perspective compared to the nominalizer の.

When こと is used as a nominalizer, it transforms an entire clause into a noun phrase. Compared to the nominalizer の, こと conveys a sense of emotional distance or abstraction — the speaker treats the event as a general concept rather than something directly witnessed or personally felt. For instance, 彼が来ることを知っている presents the fact objectively, while 彼が来るのを見た implies direct sensory experience. こと is required in certain grammatical contexts, such as before です/だ for definitions, and in set phrases like ことにする and ことができる. の is preferred with perception verbs like 見る, 聞く, and 感じる.

例文

  1. 毎日運動することが大切です。
  2. 彼が合格したことを聞いた。
  3. 早く寝ることにしました。

使い方ガイド

場面: spoken, written, everyday

トーン: descriptive

正しい言い方

  • 本を読むことが趣味です。
  • 約束を守ることは信頼につながる。
  • 彼が転職したことを最近知った。

避ける言い方

  • 日本に行ったのがある。(In the set expression ことがある meaning 'have the experience of,' こと cannot be replaced by の) → 日本に行ったことがある。
  • 彼女が踊っていることを見た。(With perception verb 見る for direct observation, の is more natural: 踊っているのを見た) → 彼女が踊っているのを見た。

起源と歴史

The nominalizing function of こと developed from its core meaning as an abstract noun for matters and events, becoming grammaticalized as a clause nominalizer distinct from the more empathetic の.

文化的背景

世代: All ages

社会的背景: Universal

関連フレーズ

～こと (intangible thing) A formal noun that refers to an abstract, intangible thing such as an event, fact, experience, or matter. It contrasts with もの, which typically refers to tangible objects. ～ことがある (experience) Used with the past tense of a verb to express that someone has had the experience of doing something at least once. It is equivalent to 'have done' or 'have experienced' in English. ～という (called / that says) A phrase that marks information identifying, naming, or explaining the noun that follows. It connects a descriptive clause or name to a noun, equivalent to 'called,' 'named,' or 'that says.' ～は～が (topic has attribute) A construction that relates a non-controllable state, attribute, or ability to a topic. The は marks the overall topic, while が marks the specific subject of the attribute or state being described. 連体修飾節 (Relative Clause) A clause that modifies a noun by placing a verb, adjective, or clause directly before the noun without a relative pronoun. Japanese relative clauses precede the noun they modify. ～ことがある (sometimes) Used with the dictionary form of a verb to express that something happens occasionally or from time to time. It conveys the idea that an event occurs sometimes but not regularly. ～として (as / in the capacity of) A compound particle that indicates the capacity, role, function, or status in which someone or something acts. It is equivalent to 'as' or 'in the role of' in English. ～と言えば (speaking of) An expression that presents a word or phrase as the topic of the following discourse. It is used to introduce an association or to shift the conversation to a related topic.
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