Nominalizing Actions: koto vs no｜〜こと・〜の
When transforming an action or clause into a noun phrase (equivalent to English "-ing" or "to do"), Japanese offers two fundamental nominalizers: 〜こと (koto) and 〜の (no). While both create noun phrases, they are not interchangeable. In modern spoken Japanese, the choice depends primarily on the verb or adjective that follows. Sensory perception and immediate actions usually take 〜の, whereas communication, intellectual concepts, and set grammatical patterns usually take 〜こと.
動詞を『〜すること』『〜するの』のように名詞にするときに使います。うしろに来る言葉によって『こと』と『の』を使い分けます。日常会話での使い分けを練習しましょう。
Direct sensory perception and immediate physical action: 〜の
When the following verb involves direct sensory perception (見る, 聞こえる, 感じる) or an action directly affecting an ongoing event (手伝う, 待つ, 止める), you normally use 〜の. Because 〜の evokes an immediate, tangible scene happening before your eyes, saying 赤ちゃんが泣いているのを聞いた (I heard a baby crying) is natural, while こと sounds unnatural here.
目で見たり耳で聞いたりする知覚動詞や、いま起きている行動を『手伝う』『待つ』ときは『の』を使います。
Communicative speech, conceptual thoughts, and set patterns: 〜こと
When the following verb involves communication (言う, 伝える, 知らせる), promises and thoughts (約束する, 信じる, 考える), or set grammatical formulas (〜ことができる: can do; 〜ことがある: have done), you normally use 〜こと. It frames the action as an objective topic, concept, or piece of information.
言葉で『伝える』『言う』『約束する』や、頭の中で考えること、また『〜ことができる』などの文型には『こと』を使います。
Personal preferences, emotions, and skills: 〜の is most natural
With adjectives expressing likes, dislikes, strengths, and weaknesses (好き, 嫌い, 上手, 下手, 得意, 苦手), both patterns are technically possible, but 〜の is far more frequent and natural in daily spoken Japanese: 映画を見るのが好きです sounds warm and conversational.
『好き』『嫌い』『上手』『下手』のときは、会話では『の』を使うのがとても自然です。
Summary rule for quick decision
Use 〜の for immediate physical reality and five senses. Use 〜こと for conceptual facts, verbal messages, and fixed grammatical patterns like 〜ことができる.
五感で感じることには『の』、言葉や決まりには『こと』と覚えましょう。
Examples / 例
The following scenes and exercises were written for this lesson. They do not describe an actual service or event.
私の趣味は休みの日に料理を作ることです。
My hobby is cooking meals on my days off.
Defining an abstract personal hobby or concept.
窓の外で小鳥が楽しそうに歌っているのが聞こえます。
I can hear little birds singing pleasantly outside the window.
Immediate sensory auditory perception requiring 〜の.
会議の時間を変更したことを、チーム全員にメールで伝えました。
I informed everyone on the team by email that the meeting time had changed.
Communicating factual information to others requiring 〜こと.
重い荷物をトラックへ運ぶのを手伝ってもらえませんか。
Could you please help me carry the heavy boxes to the truck?
Assisting directly in an ongoing physical action requiring 〜の.
Practice / 練習
Read each situation. Say your answer before opening “Answer and explanation.”
Q1. Expressing your love of playing tennis in casual conversation: テニスを（するの／すること）が大好きです。
Answer and explanation
するの
For expressing personal likes (好き) and hobbies in daily conversation, 〜の is the most natural choice.
Q2. You saw Tanaka-san leave the office: 田中さんが会社を出る（こと／の）を見ました。
Answer and explanation
の
Direct visual observation (見る) normally takes the nominalizer 〜の.
Q3. You promised to arrive by 10 AM: 明日10時に来る（こと／の）を約束しました。
Answer and explanation
こと
Verbs of promise (約束する) and communication take 〜こと to represent the agreed-upon content.
Q4. Can you say: "ピアノを弾くのができます" to express ability? (Yes / No)
Answer and explanation
いいえ、言えません。
No. The potential pattern "to be able to do" is a fixed grammatical idiom: 〜ことができます.
Words / 言葉
| Japanese | English |
|---|---|
| 趣味 | hobby; pastime |
| 伝える | to convey; report |
| 約束 | promise; appointment |
| 手伝う | to help; assist |
| 感覚 | sensation; sense |
A phrase to use
駅で財布を落としたのに気づいて、すぐに交番へ行きました。
I noticed that I had dropped my wallet at the station and went immediately to the police box.
Sources
Grammar reference: The Japan Foundation, Irodori: Japanese for Life in Japan. The explanations here are concise original summaries; examples and practice questions are original.
- Elementary 1, Lesson 2, grammar notes, PDF page 15
- Elementary 1, Lesson 9, grammar notes, PDF page 18
Official Irodori Elementary 1 download page · Official Irodori Elementary 2 download page