What exactly is "なの" (nano)?

Question

I asked a female Japanese friend to translate a sentence for me and it ends in "nano" which I took to be either an alternative question particle to -ne or -ka; or possibly two particles I don't know which could come together.

But just now I looked it up in wwwjdict and it tells me it's a "feminine copula". So does this mean "なの" (nano) is a synonym of "です" (desu) that only female speakers use? Assuming it's not very formal, what should I use instead as a noun?

Also does this mean it's a verb and if so what kind of conjugation or other forms does it have?

EDIT

Since this has turned out to be quite subtle and even controversial, here is my sentence:

(Original English: Why must life be so difficult?)

Japanese translation: なんで[人生]{じんせい}はそんなに[大変]{たいへん}なの？

Answer 1

Everyone's done a great job of answering this one, so I'm just going to add a quick answer. The なの that you're asking about is really just の. The な is only there if you use it after a noun or a na-adjective (きれい, 大変, 非常). The most common way of using this の is as a question marker.

そうなの - Is it really?

This is the same as そうなんですか but less formal.

何をしているの? What are you doing?

The same as 何をしているんですか. Or even less formally, 何してんの?

仕事は大変なの? - Is your work difficult?

More formally as 仕事は大変なんですか。

元気がないね。どうしたの？ - You don't seem well. What happened?

どうしたの is really common as a way of asking "What's wrong" or "What happened?"

You can use it to answer a question too (高いのよ！ - It is expensive), but I think the form you were asking about was the question form.

So for your question phrase, なんで人生はそんなに大変なの？, the の is making it a question (although it would be a question without the の) but also making it more emotional (in much the same was as のですか adds emotion). I think that women might use it without the な, even after a noun or na-adjective: 仕事は大変の?

Note here that you should only use this with kids or good friends, and that there's a rising intonation at the end.

Answer 2

なの relates to the ～のだ construction, and as such provides explanatory, secondary, or supporting information (which could be a reason, a cause, or other fact the speaker feels would aid in the listener's understanding). Note that the な is only used if the preceding word is a noun or な-adjective. Following a verb or い-adjective, only の is used:

あの公園はとてもきれいなの。 That park is beautiful.

よく見たら、その動物はどうやら猫なの。 When I took a closer look, that animal turned out to be a cat.

その後、ちょっと買い物に行ったの。 After that, I went shopping for a bit.

この宿題は本当に難しいの。 This homework is really difficult.

These sentences have a feminine sound to them; to make them more masculine, change の to んだ, or のだ in written form. んです, or のです in written form, is a polite equivalent which is also gender-neutral.

Also, while this doesn't come through in the English, the use of の implies that the preceding sentence plays a supporting role in the surrounding context. It's still important, but the role it plays is more like that of a framework which buttresses the speaker's main point. This is a somewhat delicate inflection, the complete treatment of which is beyond the scope of this question.

Answer 3

なの is kind of a conclusion used at the end of explanation with a calm/quit sense.　Example.,

彼女は大学生なのよ She is university student, you know.

It is just combination of two particles な and の.

なのです is polite form, and なの is same with なのだ just omitting だ after that.

sometime it is used as 〜なんです。

なの is used by females most of the time, but なんです may use by males too.

Answer 4

I stumbled across this question looking for something else, and I realize it's pretty old by the time I'm writing this, but while some of the answers did adequately cover the meaning/interpretation, it bugs me a bit that none of the answers actually explain what's going on grammatically here.

In your sentence, the な in なの is not a particle. It is actually a form of the verb だ/です. だ can change to な under some circumstances, such as this.

This is actually technically the same thing that is happening when you place a な-adjective in front of a noun, too. In general, in Japanese you can simply place a verb, or verb-phrase in front of a noun to make it modify that noun, like so:

• リンゴが落ちた — (An) apple fell
• 落ちたリンゴ — (The) apple which fell (落ちた is modifying リンゴ)

With the copula だ, you can technically do this too, but だ is unusual in that it can't be placed in front of something else as だ, so it ends up changing form in the process:

• 本が好きだ — (I) like the book
• 好きな本 — (The) book which (I) like

(This is actually just taking the verb-phrase 好きだ and putting it in front of 本 to modify it, the same as the previous example, but だ changes to な in the process.)

But anyway, this same changing from だ to な also happens when you add の after a phrase ending in だ. So if you have a sentence which ends in だ and you want to turn it into a question by adding の, you need to change だ to な in the process:

• 大変だ — It is difficult
• 大変なの？ — Is it difficult?

This same thing also happens when, for example, adding のです to a sentence which ends in だ/です:

• 大変です
  → 大変だ + のです
  → 大変なのです

(Or also with various other constructions which add の, such as ので, etc.)

So in this case, it is just using の as a question particle on the end of the sentence, but since the statement-form of the sentence would end with だ, when adding の for a question, it must become なの on the end instead:

• 人生はそんなに大変だ — Life is so difficult
• なんで人生はそんなに大変なの？ — Why is life so difficult?

Answer 5

**EDIT:***As per Derek's comment, I have misunderstood the meaning of copula. My examples here were all ending particles (jp: 終助詞).*

The {Noun/なAdj}-なの or {いAdj/Verb}-の ending particle has various usage, and according to くろしお出版's 日本語文型辞典, the primary users are different according to usage.

Question

Used to indicate inquiry. Inclining intonation.
User: Children as general, or ordinary people towards their close ones (friends, family).

てつお：明日どこか行くの？
Tetsuo: Are you going somewhere tomorrow?

Explanation

To explain a circumstance. Declining intonation.
User: Children, female people. Light mooded.

かなこ：うん、町内会でちょっと用事なの。
Kanako: Yeah, I've got something up with the neighbourhood association.

Assent

Confirmation expression. Intonation can be either inclining or declining.

てつお：へえ、かなこちゃんってよく町内会に参加してたの。
Tetsuo: Wow, Kanako's quite active in the association, huh. You can see that it implies a certain degree of surprise of unexpectedness.

Light volition

To express volition, either an order or a prohibition, in a light manner. Declining intonation.
User: female, towards someone of lower rank (e.g. younger people).

かなこ：そうよ。てっちゃんもいい加減町内会をサボらないの。そんなんだからいつまでたっても人見知りなのよ。ほら、明日一緒に行くの。いい？
Kanako: That's right. And Tec-chan, you ought to stop skipping association meetings. That's why you are always shy of other people. Come on, you should go together tomorrow. Oorah?

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See how the の ending particle can be replaced with similar ones. I'll be using polite form for each:

1. 明日どこか行きますか。 (の→ですか)
   
2. (a) はい、町内会で少し用事があります。(の→です)
   (b) はい、町内会で少し用事があるからです。(の→だからです)
   
3. そうですか、かなこちゃんはよく町内会に参加していましたか。(の→ですか)
   
4. てつおさんももう町内会をサボらないでください。({verb}ないの→{verb}ないでください
   
5. さあ、明日は一緒に行きなさい。({verb}の→{verb}なさい)