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.

Conjugation Tables

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.

Using: 学生 (がくせい)

Conjugated Form	Example
Dictionary Form The base form of the noun
学生がくせい	学生がくせいは勉強べんきょうが仕事しごとだ。 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	私わたしは学生がくせいだ。 I am a student.
Modifier Form Add の after the noun (before another noun)
学生のがくせいの	学生がくせいの仕事しごとは勉強べんきょうだ。 A student's job is studying.
Negative Form
学生ではないがくせいではない	彼かれは学生がくせいではない。 He is not a student.
Past Form
学生だったがくせいだった	彼女かのじょは学生がくせいだった。 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	その時とき、私わたしはまだ学生がくせいではなかった。 At that time, I was not yet a student.
Te-form (Connective)
学生でがくせいで	彼かれは学生がくせいで、毎日まいにち勉強べんきょうする。 Being a student, he studies every day.

Plain Negative (ではない vs じゃない)

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

今日きょうは雨あめではない。 / 今日きょうは雨あめじゃない。
It's not rain today.
これはペンではない。 / これはペンじゃない。
This isn't a pen.

Connecting with て-form (で)

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

彼かれは学生がくせいで、毎日まいにち勉強べんきょうする。
He is a student and studies every day.
彼女かのじょは日本人にほんじんで、先生せんせいだ。
She is Japanese and a teacher.
この部屋へやは静しずかで、快適かいてきだ。
This room is quiet and comfortable.