～くない

The ～くない form is used to express the negative present tense of i-adjectives in Japanese. It is used to indicate that a state, quality, or characteristic does not apply or is not true.

• Plain Form: Used in casual or informal speech to describe negative qualities or states.

  このほん本はたかくない高くない。

  This book is not expensive.

• Polite Form: Add です to make the statement more formal.

  そのりょうり料理はおいしくないです。

  That dish is not tasty.