Essential i-adjectives (i-keiyoushi)
I-adjectives are the most common type and the first you should master. All end in い (i) in their dictionary form and conjugate by modifying that final syllable. Learn these core i-adjectives and you will describe size, feeling, temperature, and quality in everyday conversation.
The Irregular i-adjective: いい (good)
Only one irregular i-adjective exists: いい (ii, good). It conjugates from its alternate stem よい (yoi) for all forms except the dictionary form. This pattern appears frequently in conversation, so memorize it early.
Common i-adjective Patterns
I-adjectives follow predictable patterns once you understand the core forms. Size adjectives (大きい, 小さい), temperature words (熱い, 冷たい), and descriptive terms (新しい, 古い) all use the same conjugation rules.
- 高い (takai) - tall, expensive
- 低い (hikui) - low, short in height
- 安い (yasui) - cheap, inexpensive
- 大きい (ookii) - big, large
- 小さい (chiisai) - small, little
- 新しい (atarashii) - new
- 古い (furui) - old (for objects, not people)
- 熱い (atsui) - hot (to the touch)
- 冷たい (tsumetai) - cold (to the touch)
- 暑い (atsui) - hot (weather/climate)
- 寒い (samui) - cold (weather/climate)
- 面白い (omoshiroi) - interesting, funny
- 楽しい (tanoshii) - fun, enjoyable
- 難しい (muzukashii) - difficult
- 易しい (yasashii) - easy
- いい / よい (ii / yoi) - good (irregular, conjugates from yoi)
- 悪い (warui) - bad
| Term | Meaning | Pronunciation | Example |
|---|---|---|---|
| 高い | Tall / Expensive (i-adjective) | takai | この山は高いです。(Kono yama wa takai desu.), This mountain is tall. |
| 低い | Low / Short in height (i-adjective) | hikui | 天井が低いです。(Tenjou ga hikui desu.), The ceiling is low. |
| 安い | Cheap / Inexpensive (i-adjective) | yasui | このカフェは安いです。(Kono kafe wa yasui desu.), This cafe is cheap. |
| 大きい | Big / Large (i-adjective) | ookii | 大きい犬がいます。(Ookii inu ga imasu.), There is a big dog. |
| 小さい | Small / Little (i-adjective) | chiisai | 小さい箱をください。(Chiisai hako o kudasai.), Please give me the small box. |
| 新しい | New (i-adjective) | atarashii | 新しい車を買いました。(Atarashii kuruma o kaimashita.), I bought a new car. |
| 古い | Old (for objects, not people) (i-adjective) | furui | この本は古いです。(Kono hon wa furui desu.), This book is old. |
| 熱い | Hot (to the touch) (i-adjective) | atsui | お茶が熱いです。(Ocha ga atsui desu.), The tea is hot. |
| 冷たい | Cold (to the touch) (i-adjective) | tsumetai | 冷たい水をお願いします。(Tsumetai mizu o onegaishimasu.), Cold water, please. |
| 暑い | Hot (weather/climate) (i-adjective) | atsui | 今日は暑いですね。(Kyou wa atsui desu ne.), It's hot today, isn't it? |
| 寒い | Cold (weather/climate) (i-adjective) | samui | 冬は寒いです。(Fuyu wa samui desu.), Winter is cold. |
| 面白い | Interesting / Funny (i-adjective) | omoshiroi | この映画は面白いです。(Kono eiga wa omoshiroi desu.), This movie is interesting. |
| 楽しい | Fun / Enjoyable (i-adjective) | tanoshii | 旅行は楽しかったです。(Ryokou wa tanoshikatta desu.), The trip was fun. |
| 難しい | Difficult (i-adjective) | muzukashii | 日本語は難しいです。(Nihongo wa muzukashii desu.), Japanese is difficult. |
| 易しい / 簡単 | Easy (yasashii is i-adj; kantan is na-adj) | yasashii | このテストは易しかったです。(Kono tesuto wa yasashikatta desu.), This test was easy. |
| いい / よい | Good (irregular i-adjective, conjugates from yoi) | ii / yoi | 今日は天気がいいです。(Kyou wa tenki ga ii desu.), The weather is good today. |
| 悪い | Bad (i-adjective) | warui | 頭が悪いですが、頑張ります。(Atama ga warui desu ga, ganbarimasu.), I'm not smart, but I'll do my best. |
Essential na-adjectives (na-keiyoushi)
Na-adjectives behave grammatically more like nouns than adjectives. When they modify a noun directly, you must insert な between them. For example: 元気な子供 (genki na kodomo, an energetic child).
At the end of a sentence, na-adjectives use desu: 元気です (genki desu, I'm well). To negate, use ja arimasen or ja nai.
False i-adjectives: Watch for These Exceptions
A few na-adjectives end in い, which confuses learners. 綺麗 (kirei, pretty) and 嫌い (kirai, disliked) are classic examples. Despite ending in い, they conjugate as na-adjectives. Memorize these exceptions early to avoid conjugation errors.
Core na-adjectives by Category
Na-adjectives cover personality, quality, and state descriptions. These 17 words form the foundation of daily Japanese conversation.
- 元気 (genki) - energetic, healthy, well
- 静か (shizuka) - quiet, calm
- 綺麗 (kirei) - pretty, beautiful, clean
- 有名 (yuumei) - famous
- 親切 (shinsetsu) - kind, friendly
- 便利 (benri) - convenient
- 不便 (fuben) - inconvenient
- 好き (suki) - liked, favorite
- 嫌い (kirai) - disliked, hated
- 上手 (jouzu) - skillful, good at
- 下手 (heta) - unskilled, bad at
- 簡単 (kantan) - simple, easy
- 大変 (taihen) - tough, difficult, serious
- 安全 (anzen) - safe
- 危険 (kiken) - dangerous
- 大切 (taisetsu) - important, precious
- 必要 (hitsuyou) - necessary
| Term | Meaning | Pronunciation | Example |
|---|---|---|---|
| 元気 | Energetic / Healthy / Well (na-adjective) | genki | 彼は元気な人です。(Kare wa genki na hito desu.), He is an energetic person. |
| 静か | Quiet / Calm (na-adjective) | shizuka | 静かな部屋ですね。(Shizuka na heya desu ne.), It's a quiet room. |
| 綺麗 | Pretty / Beautiful / Clean (na-adjective, despite ending in い) | kirei | 綺麗な花ですね。(Kirei na hana desu ne.), What beautiful flowers. |
| 有名 | Famous (na-adjective) | yuumei | 京都は有名な街です。(Kyouto wa yuumei na machi desu.), Kyoto is a famous city. |
| 親切 | Kind / Friendly (na-adjective) | shinsetsu | あの店員は親切です。(Ano ten'in wa shinsetsu desu.), That shop clerk is kind. |
| 便利 | Convenient (na-adjective) | benri | このアプリは便利です。(Kono apuri wa benri desu.), This app is convenient. |
| 不便 | Inconvenient (na-adjective) | fuben | 駅から遠くて不便です。(Eki kara tookute fuben desu.), It's inconvenient because it's far from the station. |
| 好き | Liked / Favorite (na-adjective) | suki | 寿司が好きです。(Sushi ga suki desu.), I like sushi. |
| 嫌い | Disliked / Hated (na-adjective, despite ending in い) | kirai | 虫が嫌いです。(Mushi ga kirai desu.), I dislike bugs. |
| 上手 | Skillful / Good at (na-adjective) | jouzu | 日本語が上手ですね。(Nihongo ga jouzu desu ne.), You're good at Japanese. |
| 下手 | Unskilled / Bad at (na-adjective) | heta | 料理が下手です。(Ryouri ga heta desu.), I'm bad at cooking. |
| 簡単 | Simple / Easy (na-adjective) | kantan | この問題は簡単です。(Kono mondai wa kantan desu.), This question is easy. |
| 大変 | Tough / Difficult / Serious (na-adjective) | taihen | 仕事が大変です。(Shigoto ga taihen desu.), Work is tough. |
| 安全 | Safe (na-adjective) | anzen | 日本は安全な国です。(Nihon wa anzen na kuni desu.), Japan is a safe country. |
| 危険 | Dangerous (na-adjective) | kiken | ここは危険です。(Koko wa kiken desu.), It's dangerous here. |
| 大切 | Important / Precious (na-adjective) | taisetsu | 家族は大切です。(Kazoku wa taisetsu desu.), Family is important. |
| 必要 | Necessary (na-adjective) | hitsuyou | 練習が必要です。(Renshuu ga hitsuyou desu.), Practice is necessary. |
Conjugating Japanese Adjectives: Tense and Negation
Once you identify whether an adjective is i-type or na-type, conjugation follows predictable rules. I-adjectives change their own ending, while na-adjectives rely on the copula desu. These four essential forms unlock all tenses: present affirmative, present negative, past affirmative, and past negative.
How i-adjectives Change
I-adjectives drop the い and add specific suffixes. Present negative uses くない. Past affirmative uses かった. These rules apply consistently to almost every i-adjective.
How na-adjectives Change
Na-adjectives stay the same but attach different forms of the copula. Use ja nai or ja arimasen for negation. Use datta (informal) or deshita (polite) for past tense. The na-adjective itself never changes.
Essential Conjugation Forms
- 高い → 高くない (takai → takakunai): drop い, add くない
- 高い → 高かった (takai → takakatta): drop い, add かった
- 高い → 高くなかった (takai → takakunakatta): drop い, add くなかった
- いい → よくない (ii → yokunai): irregular, conjugates from yoi
- いい → よかった (ii → yokatta): irregular past form
- 静か → 静かじゃない (shizuka → shizuka ja nai): na-adj negative with ja nai
- 静か → 静かだった (shizuka → shizuka datta): na-adj past, informal
- 静か → 静かでした (shizuka → shizuka deshita): na-adj past, polite
- 綺麗 → 綺麗じゃなかった (kirei → kirei ja nakatta): na-adj past negative
- 大きい + 部屋 (ookii heya): i-adjectives modify nouns directly
- 有名 + な + 人 (yuumei na hito): na-adjectives need な before nouns
- 面白く + ない (omoshirokunai): connecting i-adjective stem with another word
- 楽しくて (tanoshikute): i-adjective て-form, drop い, add くて
- 静かで (shizuka de): na-adjective て-form, add で
- 暑く + なる (atsuku naru): i-adjective adverb form, drop い, add く
| Term | Meaning | Pronunciation | Example |
|---|---|---|---|
| 高い → 高くない | Expensive → Not expensive (i-adj negative: drop い, add くない) | takai → takakunai | このカフェは高くないです。(Kono kafe wa takakunai desu.), This cafe is not expensive. |
| 高い → 高かった | Expensive → Was expensive (i-adj past: drop い, add かった) | takai → takakatta | 昔は高かったです。(Mukashi wa takakatta desu.), It was expensive in the past. |
| 高い → 高くなかった | Expensive → Was not expensive (i-adj past negative) | takai → takakunakatta | 思ったより高くなかったです。(Omotta yori takakunakatta desu.), It wasn't as expensive as I thought. |
| いい → よくない | Good → Not good (irregular; conjugates from yoi) | ii → yokunai | 体の調子がよくないです。(Karada no choushi ga yokunai desu.), I'm not feeling well. |
| いい → よかった | Good → Was good (irregular past form) | ii → yokatta | 映画はよかったです。(Eiga wa yokatta desu.), The movie was good. |
| 静か → 静かじゃない | Quiet → Not quiet (na-adj negative with ja nai) | shizuka → shizuka ja nai | この町は静かじゃないです。(Kono machi wa shizuka ja nai desu.), This town isn't quiet. |
| 静か → 静かだった | Quiet → Was quiet (na-adj past, informal) | shizuka → shizuka datta | 昨日は静かだった。(Kinou wa shizuka datta.), Yesterday was quiet. |
| 静か → 静かでした | Quiet → Was quiet (na-adj past, polite) | shizuka → shizuka deshita | 図書館は静かでした。(Toshokan wa shizuka deshita.), The library was quiet. |
| 綺麗 → 綺麗じゃなかった | Pretty → Was not pretty (na-adj past negative) | kirei → kirei ja nakatta | 部屋は綺麗じゃなかったです。(Heya wa kirei ja nakatta desu.), The room wasn't clean. |
| 大きい + 部屋 | Big + room = big room (i-adj directly modifies noun) | ookii heya | 大きい部屋を予約しました。(Ookii heya o yoyaku shimashita.), I reserved a big room. |
| 有名 + な + 人 | Famous + na + person = famous person (na-adj needs な) | yuumei na hito | 有名な人に会いました。(Yuumei na hito ni aimashita.), I met a famous person. |
| 面白く + ない | Connecting i-adj stem with another word | omoshirokunai | この本は面白くない。(Kono hon wa omoshirokunai.), This book isn't interesting. |
| 楽しくて | Fun and... (i-adj て-form: drop い, add くて) | tanoshikute | 楽しくて美味しかったです。(Tanoshikute oishikatta desu.), It was fun and delicious. |
| 静かで | Quiet and... (na-adj て-form: add で) | shizuka de | 静かで綺麗な場所です。(Shizuka de kirei na basho desu.), It's a quiet and clean place. |
| 暑く + なる | To become hot (i-adj adverb form: drop い, add く) | atsuku naru | 夏は暑くなります。(Natsu wa atsuku narimasu.), It gets hot in summer. |
How to Study Japanese Effectively
Mastering Japanese requires the right study approach, not just more hours. Research in cognitive science shows three techniques produce the best results: active recall (testing yourself rather than re-reading), spaced repetition (reviewing at scientifically-optimized intervals), and interleaving (mixing related topics rather than studying one in isolation).
FluentFlash is built around all three. When you study Japanese adjectives with our FSRS algorithm, every term is scheduled for review at exactly the moment you are about to forget it. This maximizes retention while minimizing study time.
Why Passive Review Fails
Re-reading your notes, highlighting textbook passages, or watching lecture videos feels productive but delivers poor results. Studies show these methods produce only 10 to 20 percent of the retention that active recall achieves. Flashcards force your brain to retrieve information, which strengthens memory pathways far more than recognition alone. Pair this with spaced repetition scheduling, and you learn in 20 minutes a day what would take hours of passive review.
A Practical 3-Week Study Plan
Start by creating 15 to 25 flashcards covering the highest-priority adjectives. Review them daily for the first week using our FSRS scheduling. As cards become easier, intervals automatically expand from minutes to days to weeks. This approach keeps you working on material at the edge of your knowledge.
- Generate flashcards using FluentFlash AI or create them manually from your notes
- Study 15 to 20 new cards per day, plus scheduled reviews
- Use multiple study modes (flip, multiple choice, written) to strengthen recall
- Track your progress and identify weak topics for focused review
- Review consistently. Daily practice beats marathon sessions
- 1
Generate flashcards using FluentFlash AI or create them manually from your notes
- 2
Study 15-20 new cards per day, plus scheduled reviews
- 3
Use multiple study modes (flip, multiple choice, written) to strengthen recall
- 4
Track your progress and identify weak topics for focused review
- 5
Review consistently, daily practice beats marathon sessions