No desu のです

Predicting phrase which strength is the preceding statement or Boston the town of a suggestion requests, or demand.

No desu is often abbreviated to n desu in colloquial speech.

1. after dictionary form a verb/ adjective

ちょっとたずねたいことがあるんですが。

Chotto tazunetai koto ga aru n desu ga.

I have a small question that I want to ask you, but… (can you help me?) 

今とても忙しいんです。

Ima totemo isogashii n desu.

I am very busy now (so I can’t help you).

2.After ta-form a verb/ adjective

さっき彼女に電話したのですが出ませんでした。

Sakki kanojo ni denwa shita no desu ga demasen deshita.

I telephoned her a little while ago, but she didn't answer.

( proceed proceeded  past tense sentence, a contrary statement usually follows)

あの自転車は安かったのですが、お金が足りませんでした。

Ano jitensha wa yasukatta no desu ga, okane ga tarimasen deshita.

That bicycle was cheap, but I didn't have enough money.

3.After nai-form of verb/ adjective

次の休暇はどこにも行かないのですか。

Tsugi no kyuuka wa doko ni mo ikanai no desu ka.

 Won't you go anywhere during the next vacation?

4. after( adjectival) noun + na/datta

今日はとてもひまなんです。

Kyou wa totemo hima-na n desu.

I am very free today (and I'm wondering what to do).

昨日はひまだったんですが、うちにいました。

Kinou wa hima datta n desu ga, uchi ni imashita.

I was free yesterday, but I stayed at home.

5.Used in question

(A question using this phrase is usually asking for some explanation, while a question without it may indicate a request or invitation. When interrogative words are used in question, no desu ka usually comes at the end of the question to clearly indicate that some information is being asked for.)

どうしてここへ来たんですか。

Doushite koko e kita n desu ka.

Why (or how) did you come here?

テニスはするんですか。

Tenisu wa suru n desu ka.

Do you play tennis?

(compare with tenisu o shimasu ka, meaning “Will you play tennis?”)

お酒は飲まないんですか。

Osake wa nomanai n desu ka.

Don’t you drink alcohol?