日本語 Japanese Ask Questions Thread 3

If you have a question about the language, ask it and fellow 4channers might see it and answer it for you.


Japanese Ask Questions Thread2
http://dis.4chan.org/read/lang/1206158123/1-40

Here's one: The phrase
どうしたの？
means "what's the matter?"
What's the role of の in the sentence? Is it a nominalization?