Just like the particle は, it can take some time to get the hang of understanding and using the Japanese particle の。I’ll use what I’ve learned from textbooks, from experience, and from dictionary.goo.ne.jp to illustrate the many uses of this important element of the language.
1) Possessive or descriptive
This is by far the easiest to understand and start using yourself almost immediately. You’ve likely read about this use elsewhere so I’ll just give a quick example to summarize:
- I lost my book.
- Please give me mine.
2) Convert a verb or verb phrase into a noun
This use is also quite simple. Here の is added to the end of a verb to turn it into noun, which can then be used by another verb.
- Let’s stop watching this movie.
3) Replacement for が
In an embedded clause, の can replace が. I feel that it de-emphasizes the subject before it compared to using が。
- The banana he ate was rotting.
4) Assertion / Emphasis (のだ）
If のだ is added after a verb (or なのだ after a noun), it has the effect of emphasizing or asserting the statement. In spoken language these are often abbreviated as んだ and なんだ.
- I’ll (do it and) show you!
Comment: Here the の (abbreviated as ん）is being used to show the speaker is insisting he/she will do something.
- I see they lost.
Comment: This usage is common when the speaker learns of new factual information. Here you can imagine he/she was watching TV and discovers their favorite football team lost. Depending on the tone used, it can imply resignation. A common expression with this is “そうなんだ” which is when you learn something new and acknowledge it, like saying “is that a fact?” as a rhetorical question.
5) For a question
の can be put after a verb in order to ask a question. In the first two examples below I feel that the sentence is more natural with の, but in the last one it can be omitted without any problem.
- Why aren’t you going?
- Are you sure its OK (with you)?
- Is it (really) OK to trust her?
If you want to use this pattern with a noun or Na-adjective, you need to put a な before the の。
- Why a dog?
6) To explain a factual reason
When used with （だ）から, の can be used to explain a factual reason.
- Because (the fact is that) you are not a baby….
Comment: This phrase can be used to scold someone who is old enough to understand or do something properly.
7) To aggressively explain a fact to someone.
The form（な)んだよ can be used to forcefully explain that something is a fact to someone else. Use it with caution.
- (The fact is that) I’m also trying (my best) !
Comment: だって here is being used as an emphatic version of も.
- What the h*** is this!?
Comment: The first なん is from 何 (“what”), whereas the second is the short form of なの. This is a very emphatic phrase to be used when you are not happy about something.
There are a few other less common uses but I think the above covers most of the frequent uses.
The way I understand and remember usages #4, #5, #6, and #7 is that adding の／ん is like saying “it’s a fact”. Try thinking to yourself “Its a fact that….” or (for a question) “Is it a fact that….?” in order to get a better feeling for what の is trying to convey.
For advanced learners, I highly recommend reading the links in the references section below which show dictionary definitions and sample sentences of many of these uses, in Japanese.
I hope this article helped to demystify some of the uses of の。