Talk:のだ

An explanation of the phrase のだ

Meaning/Function: 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.

English equivalents: The explanation is that ~; The reason is that ~; The fact is that; It is that ~

Key sentences:

1. Sentence (informal)†: 何(なに)をしているん/のですか‡。 ― nani o shite iru n / no desu ka‡. ― What are you doing? (literally, “What is it that you are doing?”)
2. Sentence (informal)†: 日本語(にほんご)を勉強(べんきょう)しているん/のです⁑。 ― nihongo o benkyōshite iru n / nodesu⁑. ― I’m studying Japanese (literally, “It is that I’m studying Japanese.”)

†だ after na-Adjective stem and Noun changes to な.
‡Informal form: 何(なに)をしているんだい。 ― nani o shite iru n dai. ― Whaddya doing? (literally, “Whazzit you’re doing?”) (male) (see Talk:だい)
何(なに)をしているの。 ― nani o shite iru no. ― What’re you doing? (literally, “What’s that you are doing?”) (female) (see Talk:の)
⁑Informal form: …勉強(べんきょう)しているんだ。 ― …benkyōshite iru n da. ― I’m studyin’…. (literally, “Izzat I’m studyin’….”) (male)
…勉強(べんきょう)しているの。 ― …benkyōshite iru no. ― I am studying…. (literally, “That I am studying….”) (female)

Formation:

1. (Verb/i-Adjective) informal のだ
   

   (話(はな)す/話(はな)した)のだ ― (hanasu / hanashita) no da ― someone (will) talk/talked (literally, “it is that someone (will) talk/talked”)
   

   (高(たか)い/高(たか)かった)のだ ― (takai / takakatta) no da ― something is/was expensive (literally, “it is that something is/was expensive”)
2. (na-Adjective stem/Noun) (な/だった) のだ
   (静(しず)かな/静(しず)かだった)のだ ― (shizukana / shizukadatta) no da ― something is/was quiet (literally, “it is that something is/was quiet”)
   (先生(せんせい)な/先生(せんせい)だった)のだ ― (sensei na / sensei datta) no da ― someone is/was a teacher (literally, “it is that someone is/was a teacher”)

Examples:

1. A: どうしてお酒(さけ)を飲(の)まないんですか。 ― dōshite o-sake o nomanai n desu ka. ― Why don't you drink sake? (literally, “Why is it you don’t drink sake?”)
   B: 私(わたし)はまだ十七(じゅうしち)なんです。 ― watashi wa mada jūshichi na n desu. ― I’m still seventeen. (literally, “The reason is I’m still seventeen.”)
2. 僕(ぼく)は今日(きょう)のパーティーに行(い)けません。宿題(しゅくだい)がたくさんあるんです。 ― boku wa kyō no pātī nīkemasen. shukudai ga takusan aru n desu. ― I can't go to today's party. I have a lot of homework. (literally, “I can't go to today's party. The reason is I have a lot of homework.”)
3. あなたと結婚(けっこん)したいんです。 ― anata to kekkonshitai n desu. ― I want to marry you. (literally, “The fact is I want to marry you.”)

Notes:

1. In conversation, のだ/です often becomes んだ/です. In informal speech, male speakers use んだ and female speakers use の. (For the informal forms of のだ in interrogative sentences, see Talk:かい and Talk:だい.)
2. Basically, we use Sentence のだ 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 the Key Sentences, A uses のです because they are asking for an explanation about what they see B doing. B also uses のです because they are explaining their actions. In this situation, (1) is odd.
   

   (1) A: 何(なに)をしていますか。 ― nani o shite imasu ka. ― What are you doing?
   B: 日本語(にほご)を勉強(べんきょう)しています。 ― nihogo o benkyōshite imasu. ― I am 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(いまなに)をしていますか。 ― anata wa ima nani o shite imasu ka. ― What are you doing now?
   

   In Example (a), as in the Key Sentences, A uses んです because A observes that B isn't drinking sake and wants an explanation for that. And, B also uses んです because he is explaining about what A observed. In Example (b), the speaker uses んです in the second sentence because it is an explanation about the information which has been given in the first sentence.
3. We also use Sentence のだ when the speaker and the hearer are not sharing information, and the speaker is not explaining or asking for an explanation about anything. In this case, the speaker is talking as if they were sharing some information 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 their ideas upon the hearer or, at least, to emphasize their ideas emotively. (See (5) below.)
   Examples:
   (3) 今日(きょう)フットボールがあるんですが一緒(いっしょ)に行(い)きませんか。 ― kyō futtobōru ga aru n desu gaisshoni ikimasen ka. ― There is a football game today. Wouldn't you like to go (together) with me? (literally, “The fact is there is a football game today. Won’t you go (together) with me?””)
   (4) 先生(せんせい)、困(こま)っているんです。助(たす)けてください。 ― sensei, komatte iru n desu. tasukete kudasai. ― Teacher, I'm in trouble. Please help me. (literally, “Teacher, the fact is I’m in trouble. Please help me.”)
   (5) 日本語(にほんご)の文法(ぶんぽう)は難(むずか)しいですがおもしろいんですよ。 ― nihongo no bunpō wa muzukashī desu gaomoshiroi n desu yo. ― Japanese grammar is difficult, but it is interesting, you know. (literally, “The fact is Japanese grammar is difficult, but it is interesting, you know.”)

Makino, Seiichi, and Michio Tsutsui. A Dictionary of Basic Japanese Grammar. Tokyo, The Japan Times, Ltd., 1994, pp. 325-328.

Wise Bridges Fool Walls (talk) 15:26 10 March 2025 (UTC) Wise Bridges Fool Walls (talk) 19:26, 10 March 2025 (UTC)