～くなかった

The ～くなかった form is the plain negative past tense of i-adjectives in Japanese. It is used to describe qualities or states that did not apply in the past.

• Negative Past: Indicates that a quality or state was not true or did not occur in the past.

  きのう昨日のてんき天気はさむくなかった寒くなかった。

  Yesterday's weather was not cold.

• Polite Form: Add です to make the statement polite and suitable for formal contexts.

  そのりょうり料理はおいしくなかったです。

  That dish was not tasty.