Japanese has two kinds of adjectives, and they behave differently. Learning which is which from the start saves a great deal of correction later.
The two types
い-adjectives end in い and change their own ending: たかい (expensive), やすい (cheap), おおきい (big), あたらしい (new), いそがしい (busy).
な-adjectives need な before a noun and behave like nouns: しずか (quiet), べんり (convenient), ゆうめい (famous), だいじょうぶ (fine), じょうず (skilled).
The trap
Some な-adjectives end in い: きれい (pretty, clean), ゆうめい (famous), きらい (disliked).
They are not い-adjectives. きれい conjugates as きれいです / きれいじゃないです, never きれくないです.
These three are worth memorising as exceptions on day one.
The four forms
| い-adjective (たかい) | な-adjective (しずか) | |
|---|---|---|
| Present | たかいです | しずかです |
| Negative | たかくないです | しずかじゃないです |
| Past | たかかったです | しずかでした |
| Past negative | たかくなかったです | しずかじゃなかったです |
And before a noun: たかい くるま / しずかな へや.
いい is irregular and it is the commonest adjective in the language: いい, よくない, よかった, よくなかった. The negative and past forms are built from よ, not い.
Joining adjectives
To say “cheap and delicious”:
- い-adjective → replace い with くて: やすくて おいしい
- な-adjective → add で: しずかで きれい
This appears constantly in the JFT-Basic and N4 grammar sections.
Adverbs
- い-adjective → replace い with く: はやい → はやく (quickly)
- な-adjective → add に: しずか → しずかに (quietly)
はやく きて ください - please come quickly.
The ones you actually need first
For JFT-Basic and N5, the high-frequency set: おおきい / ちいさい, たかい / やすい, あたらしい / ふるい, いい / わるい, あつい / さむい, おいしい, たのしい, いそがしい, むずかしい, かんたん(な), しずか(な), べんり(な), だいじょうぶ(な), たいへん(な).
Learn each one with its pair where it has one. Opposites are a standard question type in the vocabulary section: the script and vocabulary section.
How to practise
Describe your own surroundings out loud, in past and negative: 部屋は きれいじゃなかったです。仕事は たいへんでした。
Producing the conjugations about real things fixes them far faster than drilling tables. Then test them under time pressure with the free practice test, which explains every answer in your own language.