だ

(Da)

is / am / are (plain copula).

Connection rules

＋Noun or na-adjective + だ
＋Dropping だ at the end of a sentence is common in casual female speech and gender-neutral speech.
＋Before certain particles and grammatical markers, だ is required even where it would otherwise be dropped.

これは本ほんだ。

Kore wa hon da.

This is a book. (plain)

「is / am / are (plain copula)」

彼かれは学生がくせいだと思おもう。

Kare wa gakusei da to omou.

I think he's a student.

「is / am / are (plain copula)」