Japanese adjectives belong mainly to two classes: い adjectives and な adjectives. Both can describe a noun or form the predicate of the sentence, but they use different patterns. Before a noun, the い adjective keeps the い, while the な adjective takes な.
The practical rule is to compare 新しい本 (atarashii hon, “new book”) with 静かな町 (shizuka na machi, “quiet city”). At the end of the sentence, we have 本は新しいです (“the book is new”) and 町は静かです (“the city is quiet”). Recognizing the adjective class is the first step to choosing the correct form.
What are the types of adjectives in Japanese?
The two main groups get their names from the form used with a noun. This is more accurate than just thinking about the last letter of the word.
| Class | Before the noun | As predicate |
|---|---|---|
| い adjective | Expensive store takai mise expensive store | 店は高いです。 The store is expensive. |
| な adjective | Quiet store shizuka na mise quiet store | 店は静かです。 The store is quiet. |
O Irodori exercise material, from the Japan Foundation, presents exactly the contrast ナA-な N and イA-い N, in addition to the predicative and negative forms.
Not every word that ends graphically in い is an い adjective. きれい (kirei, “beautiful; clean”) and 有名 (yūmei, “famous”), for example, are な adjectives: a clean room and 有名な人. Therefore, learn each word with its class.
How to use adjectives before nouns
When the adjective directly modifies a noun, it comes before it. い adjectives appear in the appropriate form and connect to the noun without a particle:
- blue sky
aoi sora
blue sky - not new car
atarashikunai kuruma
car that is not new - expensive store
takakatta mise
store that was expensive
な adjectives use な in the affirmative non-past form before the noun:
- 静かな町
shizuka na machi
quiet city - Convenient app
benri na apuri
practical app - lively town
nigiyaka datta machi
town that was lively
Notice the difference in meaning: that was a blue book means “that is the book that was blue”. To simply say “the book was blue”, use 本は青かったです. The past tense inside the noun phrase describes the book; the past tense in the predicate describes the state of the book in the main clause.
O Irodori formation chart also distinguishes ナA-な in イA-い before another element, reinforcing that the two classes do not connect in the same way.
How to use adjectives at the end of the sentence
In the predicate, the adjective describes the topic or subject presented in the sentence. The basic structure is [topic] + は + [adjective]. To understand how this pattern fits into the rest of the clause, see the method of Japanese sentence formation.
With い adjectives, the inflection appears on the adjective itself. In polite style, です can come after the full form:
| Form | Form with 高い | Translation |
|---|---|---|
| Non-past affirmative | 高いです | It's expensive. |
| Non-past negative | 高くないです | It's not expensive. |
| Affirmative past | 高かったです | It was expensive. |
| negative past | 高くなかったです | It was not expensive. |
With な adjectives, the final part of the predicate changes. It is not correct to summarize this by saying they “do not inflect” and need a verb: the predicative pattern has its own forms.
| Form | Form with 静か | Translation |
|---|---|---|
| Non-past affirmative | It is quiet | It is quiet. |
| Non-past negative | 静かじゃないです | It is not quiet. |
| Affirmative past | It was quiet (polite) | It was quiet. |
| negative past | 静かじゃなかったです | It was not quiet. |
THE Marugoto conjugation table, also from the Japan Foundation, organizes these forms into non-past/past and affirmative/negative. To delve into each class separately, consult the guides for い adjectives and な adjectives.
What is the role of です after an adjective?
After an い adjective, です adds politeness; the adjective already carries the inflection. Therefore, it was expensive is incorrect: the past is 高かったです.
With な adjectives in the polite predicate, we find forms like It is quiet and It was quiet (polite). In the plain style, they appear as 静かだ, It was quiet, It is not quiet and It was not quiet. The guide on です in Japanese explains the difference between politeness, word class, and tense.
Note the adjective いい
いい (ii, “good”) is irregular. In the affirmative non-past form, use いい; in other inflections, the base is よい:
- いいです — it is good;
- よくないです — it is not good;
- よかったです — it was good;
- よくなかったです — it was not good.
The same change appears in compounds ending in いい, like かっこいい: かっこよかったです (“was cool; looked good”).
Common mistakes with Japanese adjectives
- Adding な to an い adjective: say Expensive store, not 高いな店.
- Removing な from a な adjective before a noun: say 静かな町, not 静か町.
- Sort by visual ending: きれい it is a な adjective, despite the い ending.
- Making the past tense as it was expensive: use 高かったです.
- Confusing modification and predication: 青かった本 is “the book that was blue”; 本は青かったです is “the book was blue”.
Short dialogue with adjectives
A: 新しい町はどうですか。
Atarashii machi wa dō desu ka.
How is the new city?
B: 便利で、にぎやかです。でも、家賃は安くないです。
Benri de, nigiyaka desu. Demo, yachin wa yasukunai desu.
It's convenient and lively. But the rent is not cheap.
A: 前の町は静かでしたか。
Mae no machi wa shizuka deshita ka.
Was the previous city quiet?
B: はい、とても静かでした。
Hai, totemo shizuka deshita.
Yes, it was very quiet.
Exercise: complete with the appropriate form
- 静か___部屋 — a quiet room.
- この本は高___です。 — this book was expensive.
- きれい___公園 — a beautiful park.
- 昨日の映画はよ___です。 — yesterday's movie was good.
- この道は広___です。 — this street is not wide.
Answers: 1) 静かな部屋, because 静か is a な adjective; 2) 高かったです, past of 高い; 3) きれいな公園, because きれい is a な adjective; 4) よかったです, irregular past of いい; 5) 広くないです, negative of 広い.
Common questions
What are the types of adjectives in Japanese?
The two main groups are the い-adjectives and the な-adjectives. Before a noun, い-adjectives keep the い, as in 高い店, while な-adjectives take な, as in 静かな店.
How to know if a Japanese adjective is い or な?
The ending helps, but it's not enough. Learn the word along with the form used before a noun. Words like きれい and 有名 are な-adjectives, even though きれい graphically ends in い.
Why is kirei a na adjective?
In きれい, the い at the end is part of the word and is not the inflectable ending of い-adjectives. Therefore, before a noun we use きれいな, as in きれいな部屋.
Can I use desu after an i-adjective?
Yes. In a polite sentence, です can come after the full form of an い adjective, as in 高いです and 高かったです. The inflection is on the adjective; therefore, 高いでした is incorrect.
How to form the negative past tense of Japanese adjectives?
With い adjectives, replace い with くなかった, as in 高くなかったです. With な adjectives, use forms like 静かじゃなかったです or 静かではありませんでした, depending on the register.
Next step: use the adjectives in complete sentences
When you encounter a new adjective, record the word with its class and practice four forms: non-past affirmative, non-past negative, past affirmative, and past negative. Then, create a sentence before a noun and another as a predicate. This exercise connects adjectives to the fundamentals of japanese grammar and to the particles that organize the sentence.