"i" adjectives end in い in their dictionary form and directly modify nouns. They conjugate similarly to verbs to express tense and polarity.
| Form | Rule | Romaji |
|---|---|---|
| Present Positive | root + い | taka |
| Present Negative | drop い + くない | taka |
| Past Positive | drop い + かった | taka |
| Past Negative | drop い + くなかった | taka |
| Adverbial | drop い + く | taka |
| Te-form | drop い + くて | taka |
- These adjectives must end in い in their dictionary form.
- They are not followed by な when modifying nouns.
- The polite form is simply followed by desu.
この山は高いです。
Kono yama wa takai desu.
This mountain is tall.
この山は高くないです。
Kono yama wa takakunai desu.
This mountain is not tall.
昨日のテストは難しかったです。
Kinou no tesuto wa muzukashikatta desu.
Yesterday’s test was difficult.
彼の話し方は優しくて、聞きやすい。
Kare no hanashikata wa yasashikute, kikiyasui.
His way of speaking is gentle and easy to listen to.
These behave like nouns and need な when directly modifying nouns.
| Form | Rule | Romaji |
|---|---|---|
| Present Positive (casual) | add だ | kirei |
| Present Positive (formal) | add です | kirei |
| Present Negative (casual) | add じゃない | kirei |
| Present Negative (formal) | add じゃありません | kirei |
| Past Positive (casual) | add だった | kirei |
| Past Positive (formal) | add でした | kirei |
| Past Negative (casual) | add じゃなかった | kirei |
| Past Negative (formal) | add じゃありませんでした | kirei |
| Adverbial | add に | kirei |
| Te-form | add で | kirei |
- Some -na adjectives end in い, like きれい, but still conjugate as na adjectives.
- Always use な before a noun.
この部屋はきれいじゃないです。
Kono heya wa kirei janai desu.
This room is not clean.
彼女の声は静かで、落ち着く。
Kanojo no koe wa shizukade, ochitsuku.
Her voice is quiet and calming.
静かに話してください。
Shizuka ni hanashite kudasai.
Please speak quietly.
Some adjectives do not follow the standard rules for -i or -na adjectives like いい or かっこいい
| Form | Conjugation | Romaji |
|---|---|---|
| Present Positive | いい / よい | ii / yoi |
| Present Negative | よくない | yokunai |
| Past Positive | よかった | yokatta |
| Past Negative | よくなかった | yokunakatta |
| Adverbial Form | よく | yoku |
| Te-form | よくて | yokute |
- Use よい for conjugation even if いい is used in writing/speaking.
- かっこいい is a compound adjective and follows the よい conjugation rules.
- "ii janai" is actually a false negative. It's a positive think such as "it's good right?!"
この映画はよかったです。
Kono eiga wa yokatta desu.
This movie was good.
彼はかっこよくないです。
Kare wa kakkoyokunai desu.
He is not cool.
天気がよくなかったです。
Tenki ga yokunakatta desu.
The weather was not good.