だ

The word だ is the informal equivalent of です. It is used in casual speech to affirm a statement about a noun or な-adjective. Unlike です, だ is not inherently polite and is mostly used among friends, peers, or in self-reflective statements.

In conversational Japanese, だ is often omitted when speaking informally, especially at the end of sentences. It is necessary with certain grammatical structures.

Negative and Past Forms

• The negative form of だ is ではない/じゃない (is not).

  がくせい学生ではない。

  I am not a student.

• The past form of だ is だった (was).

  がくせい学生だった。

  I was a student.