auxiliary
is, am, are (plain copula)
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.
(わたし)学生(がくせい)だ。
I am a student.
今日(きょう)日曜日(にちようび)だ。
Today is Sunday.
(かれ)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)

POLITE EQUIVALENT:

  • 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 (たか)い, not ×(たか)いだ)
  • Often omitted in casual speech, especially by women and in questions