no da　のだ

no da　のだ phr.

a sentence ending which indicates that the speaker is explaining or asking for an explanation about some information shared with the hearer, or is talking about something emotively, as if it were of common interest to the speaker and the hearer

The explanation is that ~ ; The reason is that ~ ; The fact is that ~ ; It is that ~

Key Sentences

A:
Sentence (informal)†
何　を　して　いる Nani o shite iru	ん/の　です n / no desu		か。‡ ka.
(What are you doing?)
B:
Sentence (informal)†
日本語　を　勉強して　いる Nihongo o benkyōshite iru		ん/の　です** n / no desu.
(I'm studying Japanese.)

†Da after Adj (na) stem and N changes to na.

‡Informal form: 何　を　して　いる　ん　だい。 (male)

Nani o shite iru n dai.

何　を　して　いる　の？ (female)

Nani o shite iru no?

**Informal form: …勉強して　いる　ん　だ。 (male)

…benkyōshite iru　n da.

…勉強して　いる　の。 (female)

…benkyōshite iru no.

Formation

(i) {V / Adj (i)} inf の　だ

no da

{話す　/話した} の　だ (s.o. (will) talk / talked)

{hanasu / hanashita} no da

{高い/高かった} の　だ (s.t. is / was expensive)

{takai / takakatta} no da

(ii) {Adj (na) stem / N} {な/だった} の　だ

{na l datta} no da

{静かな /静かだった} の　だ (s.t. is / was　quiet)

{shizukana l shizukadatta} no da

{先生　な　 /先生　だった} の　だ (s.o. is / was a teacher)

{sensei na l sensei datta} no da

Examples

(a) A: どうしてお酒を飲まないんですか

Dōshite o-sake o nomanai n desu ka.

(Why don't you drink sake?)

B: 私はまだ十七なんです。

Watashi wa mada jushichi na n desu.

((The reason is that) I'm still seventeen.)

(b) 僕は今日のパーティーに行けません。宿題がたくさんあるんです。

Boku wa kyō no pātī ni ikemasen. Shukudai ga takusan aru n desu.

(I can't go to today's party. I have a lot of homework.)

Anata to kekkonshitai n desu.

(I want to marry you.)

Notes

1. In conversation, no da / desu often becomes n da / desu. In informal speech, male speakers use n da and female speakers use no. (For the informal forms of no da in interrogative sentences, see kai and dai.)

2. Basically, S no da is used when the speaker is explaining or asking for an explanation about information shared with the hearer. The information is often what the speaker and the hearer have observed or heard. For example, in Key Sentences, A uses no desu because he is asking for an explanation about what he sees B doing. B also uses no desu because he is explaining his actions. In this situation, (1) is odd.

(1) A: 何をしていますか。

Nani o shite imasu ka.

(What are you doing?)

B: 日本語を勉強しています。

Nihongo o benkyōshite imasu.

(I'm studying Japanese.)

If, however, A is only assuming that B is doing something, A can ask the question in (2), and B can answer as B does in (1).

(2) あなたは今何をしていますか。

Anata wa ima nani o shite imasu ka.

(What are you doing now?)

In Ex. (a), as in KS, A uses n desu because A observes that B isn't drinking sake and wants an explanation for that. And, B also uses n desu because he is explaining about what A observed. In Ex. (b), the speaker uses n desu in the second sentence because it is an explanation about the information which has been given in the first sentence.

3. S no da is also used when no information is shared by the speaker and the hearer and the speaker is not explaining or asking for an explanation about anything. In this case, the speaker is talking as if some information were shared with the hearer and the effects of this are, for example,

(A) to involve the hearer in the affairs he is talking about (See (3) and (4) below.),

and / or

(B) to impose his idea upon the hearer or, at least, to emphasize his idea emotively. (See (5) below.)

Examples:

(3) 今日フットボールがあるんですが、一緒に行きませんか。

Kyō futtobōru ga aru n desu ga isshoni ikimasen ka.

(There is a football game today. Wouldn't you like to go (together) with me?)

(4) 先生、困っているんです。助けてください。

Sensei, komatte iru n desu. Tasukete kudasai.

(Teacher, I'm in trouble. Please help me.)

(5) 日本語の文法は難しいですがおもしろいんですよ。

Nihongo no bunpō wa muzukashiidesu ga omoshiroi n desu yo.

(Japanese grammar is difficult, but it is interesting, you know.)