い-Adjective + です【です (Predicate)】

An い-adjective can function directly as a predicate – that is, it can end a sentence on its own, describing the subject. To make it polite, simply add です after the い-adjective. Unlike な-adjectives and nouns, the い-adjective itself already carries predicative meaning; です is added purely for politeness and does not change the grammatical function.

Basic predicate (polite)

Place the い-adjective at the end of the sentence and add です.

In casual speech, です is simply dropped:

Negative form

To make an い-adjective negative, drop the final い and add くない. For polite speech, add です after くない.

Past form

To express the past, drop the final い and add かった. For polite speech, add です after かった.

Past negative form

Drop the final い and add くなかった. Add です for politeness.

Common mistake

Do not use だ after い-adjectives. For example, ×「高いだ」 and ×「高いだった」 are incorrect. The correct forms are たかい高い (plain) / たかいです高いです (polite) and たかかった高かった (plain past) / たかかったです高かったです (polite past).

Exception: いい / よい

The adjective いい (good) is irregular. Its conjugated forms use the stem よ: よくない (not good), よかった (was good), よくなかった (was not good).