ではない

The phrase ではない is the informal negative form of だ, meaning "is not" in English. It is used to deny or negate a statement about a noun or な-adjective.

In casual spoken Japanese, じゃない is often used instead.

Affirmative vs. Negative

• Affirmative:
  がくせい学生だ。

  I am a student.
• Negative:
  がくせい学生ではない。

  I am not a student.

Past Negative

The past negative form is ではなかった or じゃなかった.