い-Adjective

い-adjectives (also called i-adjectives) are one of the two main types of adjectives in Japanese. They are called い-adjectives because they always end in the hiragana い in their dictionary form.

Modifying nouns

い-adjectives can be placed directly before a noun to modify it, without any particle in between.

As a predicate

い-adjectives can end a sentence on their own, functioning as the predicate. Unlike な-adjectives and nouns, they do not need だ or です to form a statement – though です is added for politeness.

Conjugation

い-adjectives conjugate by dropping the final い and adding the appropriate ending:

• Negative: い → くない

  このへや部屋はひろくない広くない。

  This room is not spacious.

• Past: い → かった

  きのう昨日はさむかった寒かった。

  Yesterday was cold.

• Past negative: い → くなかった

  てすとテストはむずかしくなかった難しくなかった。

  The test was not difficult.

For polite forms, add です after each: 広くないです, 寒かったです, 難しくなかったです.

Connecting to other clauses

To connect an い-adjective to another clause (like "and"), drop い and add くて.

Common mistake: false い-adjectives

Some words end in い but are actually な-adjectives. The most common ones to watch out for are きれい (beautiful/clean), きらい嫌い (disliked), and ゆうめい有名 (famous). These follow な-adjective rules:

A helpful clue: if the い is part of the kanji reading rather than a separate hiragana ending, the word is likely a な-adjective.