い-Adjectives: Basicsい形容詞
い-adjectives (い形容詞) are one of the two main adjective types in Japanese. They always end in い in their dictionary form and conjugate by changing that final い. Unlike な-adjectives, they attach directly to nouns without any particle. Mastering い-adjectives is essential because they include some of the most common words in daily Japanese.
い-adjectives (い形容詞) are one of the two main adjective types in Japanese. They always end in い in their dictionary form and conjugate by changing that final い. Unlike な-adjectives, they attach directly to nouns without any particle. Mastering い-adjectives is essential because they include some of the most common words in daily Japanese.
What are い-adjectives?
い-adjectives are native Japanese words (和語) that describe qualities or states. They always end in the hiragana い in their dictionary form. This final い is not just decoration — it is the part that changes during conjugation. When you see an adjective ending in い, you can almost always assume it is an い-adjective (with a few famous exceptions like きれい and 嫌い, which are actually な-adjectives).
50 essential い-adjectives
Here are the most frequently used い-adjectives, organized by category. Physical qualities: 大きい (ookii, big), 小さい (chiisai, small), 高い (takai, tall/expensive), 低い (hikui, low/short), 長い (nagai, long), 短い (mijikai, short), 広い (hiroi, wide), 狭い (semai, narrow), 重い (omoi, heavy), 軽い (karui, light). Feelings: 楽しい (tanoshii, fun), 嬉しい (ureshii, happy), 悲しい (kanashii, sad), 怖い (kowai, scary), 恥ずかしい (hazukashii, embarrassing), 寂しい (sabishii, lonely). Taste/sensation: 美味しい (oishii, delicious), 甘い (amai, sweet), 辛い (karai, spicy), 苦い (nigai, bitter). Temperature/weather: 暑い (atsui, hot weather), 寒い (samui, cold weather), 熱い (atsui, hot to touch), 冷たい (tsumetai, cold to touch). Evaluation: 良い/いい (yoi/ii, good), 悪い (warui, bad), 新しい (atarashii, new), 古い (furui, old), 難しい (muzukashii, difficult), 易しい (yasashii, easy).
How to spot い-adjectives
Look at the last character. If it ends in い and is NOT one of the known exceptions (きれい, 嫌い, etc.), it is an い-adjective. Most い-adjectives are two or more kanji plus い: 美しい, 楽しい, 難しい. Single-kanji ones exist too: 良い, 無い, 酸い.
Using い-adjectives in sentences
い-adjectives serve three roles: predicate (この本は面白い — This book is interesting), noun modifier (面白い本 — an interesting book), and adverbial (速く走る — run fast, by changing い to く). As a predicate, い-adjectives do NOT need だ or です in plain speech. Adding です makes it polite: 高い (plain) → 高いです (polite). Never say 高いだ — this is a common beginner mistake.
Example sentences
この映画は面白い。
Kono eiga wa omoshiroi.
This movie is interesting.
い-adjective as predicate (plain form)
高い山が見える。
Takai yama ga mieru.
I can see a tall mountain.
い-adjective directly modifying noun (no な needed)
今日は暑いですね。
Kyou wa atsui desu ne.
It’s hot today, isn’t it?
Polite form: い + です
新しいパソコンが欲しい。
Atarashii pasokon ga hoshii.
I want a new computer.
新しい modifying パソコン; 欲しい as predicate
日本語は難しいけど楽しい。
Nihongo wa muzukashii kedo tanoshii.
Japanese is difficult but fun.
Two い-adjectives joined with けど
昨日のテストは易しかった。
Kinou no tesuto wa yasashikatta.
Yesterday’s test was easy.
Past form: い → かった
Common mistakes
高いだ
高い / 高いです
い-adjectives never take だ. Use い alone (plain) or い + です (polite). だ is only for な-adjectives and nouns.
きれいい花
きれいな花
きれい looks like an い-adjective but is actually a な-adjective. It needs な before nouns.
美味しいの寿司
美味しい寿司
い-adjectives attach directly to nouns — no の or な is needed. 美味しい寿司, not 美味しいの寿司.
面白いではない
面白くない
い-adjectives negate by dropping い and adding くない. They do not use ではない (that pattern is for な-adjectives and nouns).
Frequently asked questions
How do I know if a word ending in い is an い-adjective or a な-adjective?
Most words ending in い are い-adjectives. The exceptions are borrowed words and specific native words: きれい (clean/beautiful), 嫌い (dislike), 有名 (famous — ends in い only in some forms). A dictionary will always mark the type. As a rule of thumb, if the い is written in kanji (e.g., 嫌い where い is part of the kanji reading), be cautious.
Can I use です after い-adjectives?
Yes, adding です after an い-adjective makes it polite: 高い → 高いです. This is standard polite Japanese. However, you should NEVER add だ: 高いだ is grammatically wrong. In negative and past forms, the adjective conjugates first: 高くないです, 高かったです.
What is the difference between 熱い and 暑い? Both are "atsui."
暑い (atsui) describes hot weather or ambient temperature: 今日は暑い (It’s hot today). 熱い (atsui) describes something hot to the touch: コーヒーが熱い (The coffee is hot). Same pronunciation, different kanji, different usage.
Which of these is an い-adjective?