Noun Conjugation
Learn how nouns express 'to be' in Japanese using the copula だ, including tense, negation, and the connective て-form.
Nouns Overview
In English, nouns change form in many ways — adding -s for plurals, 's for possession, or using articles like a and the. Japanese nouns are much simpler: the noun itself never changes. There are no plurals, no grammatical gender, and no articles.
To say 'A is B' in Japanese, you attach だ (informal) or です (polite) after the noun — for example, 学生だ means 'I am a student.' It is だ that conjugates to express tense and negation, not the noun. These conjugation patterns are identical to Na-adjectives.
This page covers the plain forms of noun conjugation using だ. For polite equivalents using です, see the Polite & Plain Speech page.
The table below shows how だ changes for each tense. The noun before it stays the same every time.
Used in informal speech, casual writing, and for stating general facts.
| Conjugated Form | Example |
|---|---|
Dictionary Form The base form of the noun | |
学生がくせい | 学生は勉強が仕事だ。 For students, studying is the job. |
Plain Form Add だ after the noun (at the end of a sentence) | |
学生だがくせいだ | 私は学生だ。 I am a student. |
Modifier Form Add の after the noun (before another noun) | |
学生のがくせいの | 学生の仕事は勉強だ。 A student's job is studying. |
Negative Form | |
学生ではないがくせいではない | 彼は学生ではない。 He is not a student. |
Past Form | |
学生だったがくせいだった | 彼女は学生だった。 She was a student. |
Past Negative Form | |
学生ではなかったがくせいではなかった | その時、私はまだ学生ではなかった。 At that time, I was not yet a student. |
Te-form (Connective) | |
学生でがくせいで | 彼は学生で、毎日勉強する。 Being a student, he studies every day. |
For nouns, there are two ways to form the negative in plain Japanese. ではない is formal and common in writing or emphatic speech, while じゃない is the standard informal version used in conversation.
Examples
- It's not rain today.
今日は雨ではない。 / 今日は雨じゃない。
- This isn't a pen.
これはペンではない。 / これはペンじゃない。
The noun て-form で works like 'and' to connect noun clauses in a sentence. It lets you list multiple descriptions or reasons without ending the sentence. Each で clause adds information, and the sentence continues until the final predicate.
Examples
- He is a student and studies every day.
彼は学生で、毎日勉強する。
- She is Japanese and a teacher.
彼女は日本人で、先生だ。
- This room is quiet and comfortable.
この部屋は静かで、快適だ。