い and な adjectives

Japanese has two kinds of adjective and they behave so differently that it is best to think of them as two separate parts of speech that happen to share a job. One kind conjugates like a verb and carries its own past and negative. The other does not conjugate at all and leans on です for everything. Learn which is which as part of each word, in the same way you learned which particle goes with a verb, and the rest of this lesson is mechanical.

Telling them apart

An い adjective ends in い in its dictionary form: 高たかい, 安やすい, 新あたらしい, 大おおきい. That final い is not part of the root; it is the ending that will change when you conjugate.

A な adjective ends in anything at all, and takes な when it sits directly in front of a noun: 静しずかな, 有名ゆうめいな, 便利べんりな, 元気げんきな. Dictionaries list them without the な, so you will see 静しずか on its own and have to remember what it is.

The trap is the small group of な adjectives that end in い anyway. きれい, きらい and 有名ゆうめい all look like い adjectives and none of them is one. They conjugate with です and never by changing the い, and they take な in front of a noun: きれいな部屋へや. There are only a few, so hold them as exceptions from the start.

In front of a noun

Both kinds sit in front of the noun they describe, exactly where an English adjective sits. い adjectives attach directly. な adjectives need their な.

高たかい本ほんを買かいました takai hon o kaimashita I bought an expensive book

静しずかな部屋へやです shizuka na heya desu It is a quiet room

新あたらしい車くるまを見みました atarashii kuruma o mimashita I saw a new car

That な is the whole reason for the name. Drop it and 静しずか部屋へや is not Japanese. Add it where it does not belong and 高たかいな本ほん is not Japanese either.

い adjectives conjugate

Here is where an い adjective stops looking like an English adjective and starts looking like a verb. The final い comes off and an ending goes on. です is added at the end for politeness, but it carries no tense of its own.

このカメラは高たかいです kono kamera wa takai desu This camera is expensive

昨日きのうは寒さむくなかったです kinou wa samuku nakatta desu It was not cold yesterday

映画えいがは面白おもしろかったです eiga wa omoshirokatta desu The film was interesting

One adjective refuses to follow the pattern. いい, meaning good, conjugates from its older form よい: よくないです, よかったです, よくなかったです. いかったです does not exist. This is the only irregular adjective in the language, and it happens to be one of the most common words in it.

な adjectives borrow from です

A な adjective does not change shape at all. Everything happens in です, and the four forms are the ones you already learned in lesson ten for nouns.

この町まちは静しずかです kono machi wa shizuka desu This town is quiet

駅えきは便利べんりじゃありません eki wa benri ja arimasen The station is not convenient

先生せんせいは元気げんきでした sensei wa genki deshita The teacher was well

Read those and notice that the adjective is doing nothing. 静しずか is 静しずか in all four sentences, and every scrap of grammar is carried by the ending after it. This is why it helps to think of な adjectives as nouns: 静しずかです is built exactly like 学生がくせいです.

Joining two adjectives

To put two descriptions together, the first one takes a linking form and the last one takes the ending. い adjectives change い to くて. な adjectives take で.

この部屋へやは広ひろくて明あかるいです kono heya wa hirokute akarui desu This room is spacious and bright

静しずかで便利べんりな町まちです shizuka de benri na machi desu It is a quiet and convenient town

安やすくておいしいです yasukute oishii desu It is cheap and tasty

You cannot join them with と. と links nouns and only nouns. Using it between adjectives is one of the first mistakes an English speaker makes, and it is immediately audible.

What learners get wrong

The biggest single error is conjugating な adjectives as though they were い adjectives, usually because the word ends in い. きれいくない is not a word; きれいじゃありません is. If you are unsure which type a word is, look at whether it needs な in front of a noun. That な is the test.

The second is putting です in the middle. 高たかいですかったです comes from thinking です carries the past. It does not for い adjectives. The tense lives in the adjective and です only makes it polite, which is why 高たかかったです is right and 高たかいでした is wrong.

The third is dropping な when the adjective is in front of a noun but keeping it when it is not. 静しずかな部屋へや needs the な; 部屋へやは静しずかです must not have it.

Vocabulary

Two conjugation tables and one irregular word are the whole of Japanese adjectives, and they will not grow. What comes next is the form that connects verbs to each other in the same way くて and で connect adjectives, and it is the busiest piece of grammar in the language.