だ

だ

auxiliary

is, am, are (plain copula)

informalgrammatical

1. is, am, are (plain copula)

The plain/casual form of the copula, used to link a subject to a predicate noun or na-adjective. This is the informal equivalent of です.

私(わたし)は学生(がくせい)だ。

I am a student.

今日(きょう)は日曜日(にちようび)だ。

Today is Sunday.

彼(かれ)は先生(せんせい)だ。

He is a teacher.

だ is the plain copula in Japanese, used in casual speech and writing.

Forms

だ (plain present/future)
だった (plain past)
ではない / じゃない (plain negative)
ではなかった / じゃなかった (plain past negative)

Register

Polite equivalents

です (polite present)
でした (polite past)

Usage

Used at the end of sentences in casual/plain speech
Follows nouns and な-adjectives
With い-adjectives: だ is NOT used (say 高(たか)い, not ×高(たか)いだ)
Often dropped in casual speech, especially in questions (学生(がくせい)？ rather than 学生(がくせい)だ？) and to sound softer

Related Words

Related: です (polite copula)

general

Added 2026.2.2 19:21 · Revised 2026.10.13 22:26

09000/09496_da