Nominalizers (こと & の)
Turn verbs and clauses into noun phrases using こと and の.
Making Nouns from Verbs
In English, you can turn a verb into a noun with '-ing' (swimming is fun) or 'to' (to swim is fun). Japanese has two main nominalizers that do the same job: こと and の. Both attach to the plain form of a verb to create a noun phrase:
- 泳ぐこと — swimming / the act of swimming
- 泳ぐの — swimming
While they often overlap, each has contexts where only one is natural. Learning when to use which is one of the trickier parts of Japanese grammar.
こと turns a verb phrase into an abstract noun — 'the fact of doing' or 'the act of doing.' It attaches to the plain form of any verb (dictionary, nai, ta, or nakatta form):
[verb plain form] + こと
こと tends to sound more formal or abstract. It works well for general statements, facts, and when talking about actions as concepts.
Examples
- Speaking Japanese is fun.
日本語を話すことは楽しいです。
- Exercising every day is important.
毎日運動することが大切です。
- Do you know (the fact) that he is coming?
彼が来ることを知っていますか。
- I like traveling alone.
一人で旅行することが好きです。
の also turns a verb phrase into a noun, but it feels more immediate, personal, or concrete than こと. It's used more in casual speech and when describing something directly perceived or experienced:
[verb plain form] + の
の is especially natural with sensory verbs (見る, 聞こえる, 感じる) and emotion/preference verbs (好き, 嫌い, 上手, 下手).
Examples
- I like singing.
歌うのが好きです。
- Waking up early in the morning is tough.
朝早く起きるのはつらいです。
- I saw him crying.
彼が泣いているのを見ました。
- I can see the train coming.
電車が来るのが見えます。
Several fixed expressions require こと and do not accept の:
- ことがある — to have the experience of doing
- ことができる — to be able to do
- ことにする — to decide to do
- ことになる — it has been decided that
These are set grammatical patterns. Using の in their place would sound unnatural or change the meaning.
Examples
- I have been to Japan (before).
日本に行ったことがあります。
- She can swim.
彼女は泳ぐことができます。
- I decided to take a walk every day.
毎日散歩することにしました。
- I told my friend (the fact) that I passed the exam.
試験に受かったことを友達に伝えました。
の is required or strongly preferred in these contexts:
- Direct perception: seeing, hearing, or feeling an action happen — 見る, 聞く, 聞こえる, 見える, 感じる
- Waiting / stopping: 待つ, やめる
- Speed / timing: 早い, 遅い when describing an action
The key pattern: if you're talking about something you directly witness or physically experience in the moment, use の.
Examples
- Please stop running.
走るのをやめてください。
- I'm waiting for it to rain.
雨が降るのを待っています。
- I can hear the children playing.
子どもが遊んでいるのが聞こえます。
- He is late in coming. (His coming is slow.)
彼が来るのが遅い。
With verbs of preference (好き, 嫌い, 上手, 下手) and general statements (楽しい, 大切, 大事, 難しい), both こと and の are acceptable:
- の sounds more casual, spoken, and personal
- こと sounds more formal, written, and abstract
In everyday speech, の is more common. In writing, essays, or formal contexts, こと is preferred. Neither is wrong in these overlapping cases.
Examples
- I like playing soccer. (casual) — I like playing soccer. (formal)
サッカーをするのが好きです。
サッカーをすることが好きです。
- Cooking is fun. (casual) — Cooking is fun. (formal)
料理を作るのは楽しい。
料理を作ることは楽しい。
- I had forgotten to play the piano.
ピアノを弾くのを忘れていました。
- Keeping promises is important.
約束を守ることは大事です。
A special use of the nominalizer の is the のだ (or colloquial んだ / んです) pattern. It wraps an entire sentence in の + だ to add an explanatory or emotional nuance — 'the thing is...,' 'it's that...,' or 'you see...'
[plain form] + のだ / んです
- Explain a reason: 電車が止まったんです (It's that the train stopped)
- Seek explanation: どうしたんですか (What happened? / What's the matter?)
- Emphasize: おいしいんですよ (It really is delicious, you know)
Note: な-adjectives and nouns use なのだ / なんです (not のだ directly).
Examples
- What happened? / What's the matter?
どうしたんですか。
- Actually, (the thing is) I'm moving tomorrow.
実は、明日引っ越すんです。
- Why were you late? — (It's because) the train stopped.
なぜ遅れたんですか。
電車が止まったんです。
- This cake is really delicious, you know.
このケーキ、おいしいんですよ。