Grammar Point
particle
prt 
の

nominalizes verbs and adjectives

Informal Verb / Adjective + の

The nominalizer の is used to turn a verb or adjective phrase into a noun. It is specifically required when the speaker is describing an event or action that they are directly perceiving through their senses, such as seeing, hearing, or feeling.

Verb (Informal Form) + の

When used with a verb in the informal form, の turns the entire action into a noun phrase that can be the object of a perception verb.

I saw the cat running.

I heard someone singing.

い-Adjective (Informal Form) + の

い-adjectives in their informal form can be nominalized by の to describe a state being perceived.

I felt the room becoming cold.

な-Adjective + な + の

For な-adjectives in the present tense, な is required before adding the nominalizer の.

I watched the town become quiet.

Note

While both の and こと can nominalize phrases, の must be used with verbs of perception like 見る (to see), 聞こえる (to hear), or 待つ (to wait for). It emphasizes the immediate, physical action taking place.

Words: 
の
Radicals of radicals