Nominalization: “no” and “koto”

There are times when a verb or a phrase containing a verb needs to be thought of as a thing. Here are some
examples:
I like reading books. I like to read books. (I like the activity of reading books.)
Smoking is dangerous! (The habit of smoking is dangerous.)
I forgot that he is a teacher. (I forgot the fact that he is a teacher.)
The process of treating a phrase containing a verb as a thing (in these examples, an action/activity, a habit,
or a fact) is called “nominalization,” which means”turning something into a noun.”

In Japanese, there is a very simple way of doing this. First write the verb phrase with a plain form
(dictionary form, -ta form, -nai form, or -nakatta form). Then put either the word “no” or the word “koto”
after the phrase.

• （お酒を）飲む
  (osake o) nomu
  to drink (alcoholic beverages)
• （お酒を）飲むのが好きです。（お酒を）飲むことが好きです。
  (osake o) nomu no ga suki desu. (osake o) nomu koto ga suki desu.
  I like to drink (alcoholic beverages). I like drinking (alcoholic beverages).
• Ａについて考える
  A ni tsuite kangaeru
  to think of/about A
• 言葉について考えるのは面白い。言葉について考えることは面白い。
  kotoba ni tsuite kangaeru no wa omoshiroi. kotoba ni tsuite kangaeru koto wa omoshiroi.
  Thinking about languages is interesting.

If the verb in the phrase is a form of “to be”, “da” must be changed to “na” before “no”, and to “de aru”
before “koto”:

• 彼が先生だ
  kare ga sensei da
  he is a teacher
• 彼が先生なのを思い出しました。彼が先生であることを思い出しました。
  kare ga sensei na no o omoidashimashita. kare ga sensei de aru koto o omoidashimashita.
  I remembered that he is a teacher.
• 彼が先生だった
  kare ga sensei datta
  he was a teacher
• 彼が先生だったのを知っています。彼が先生だったことを知っています。
  kare ga sensei datta no o shitte imasu. kare ga sensei datta koto o shitte imasu.
  I know that he was a teacher.

In the sentences above, the versions with “no” have the same meaning as the versions with “koto,” but they sound more casual. The versions with “koto” are more likely to be used in writing than in speaking.
An even more casual alternative for “na no o” is to replace it by the single word “datte”:

• 彼が先生だって思い出しました。
  kare ga sensei datte omoidashimashita.
  I remembered that he is a teacher

There are many sentences, like the ones above, in which “no” and “koto” can be used interchangeably. There are situations in which one or the other must be used, however.

(A1) “no” must be used when the verb phrase expresses something sensed or perceived

• 息子が本を読んでいるのが見えます。
  musuko ga hon o yonde iru no ga miemasu. ["koto" would be wrong in this sentence.]
  I can see that my son is reading a book.

(A2) “no” must be used with verbs like yameru/tomeru (stop), matsu (wait), tetsudau (help to), jama suru
(interrupt), utsusu (change, substitute)

• つまらないから、その本を読むのを止めました。
  tsumaranai kara, sono hon o yomu no o yamemashita.
  I stopped reading the book because it was boring.

(B1) “koto” must be used when the action is talking about something, like hanasu (tell/say), tsutaeru (communicate/tell), yakusoku suru (promise), etc.

• 妹の日記を読んだことを友達に話しました。
  imouto no nikki o yonda koto o tomodachi ni hanashimashita.
  I told my friend that I read my sister’s diary.

(B2) “koto” must be used before a form of “desu” (“da”, “desu”, “de aru”, “datta”, “ja nai”, etc.)

• 問題は、妹さんの日記を黙って読んだことです。
  mondai wa, imoutosan no nikki o damatte yonda koto desu.
  The problem is that you’ve read your sister’s diary without permission.

(B3) “koto” must be used before “ga aru” to express whether something has ever happened

• 日本へ行ったことがありますか？
  nihon e itta koto ga arimasu ka?
  Have you ever been to Japan?

Short Form of “no” – “n”

The nominalization particle の (no) can in some cases in casual language be abbreviated to ん (n).

Turning the answer to a question into a thing: “ka” and “ka dou ka”

Related posts:

1. Possessive form
2. Japanese Wishes and Wants
3. Japanese Giving and Receiving