い-adjectives and な-adjectives

In Japanese, there are two types of adjectives: いi-adjectives and なna-adjectives.

The main difference between i-adjectives and な-adjectives lies in their use in a sentence.

い-adjectives

い-adjectives directly modify a noun and always end in the vowel sound “i.”
They don’t require any additional particles （助詞） to connect them to a noun.

あかい車
– a red car

For example, the i-adjective “あかい” means “red,” and it can directly modify a noun like “車” (くるま), meaning “car,” to form the phrase “あかい車” , which means “red car.”

The word form does not change even at the end of a sentence.

その車はあかい。
– The car is red.

い-adjectives
高い（たかい） high
古い（ふるい）old
小さい（ちいさい）small
眠い（ねむい）sleepy
悲しい（かなしい）sad

な-adjectives

きれい花
きれいな花
– a pretty flower

きれい /kirei/ ends with 「い」.
However, it’s not い-形容詞, so you cannot use it as 「きれい花」.
きれい is a な-adjective, so it needs 「な」at the end, as in 「きれいな花」.

At the end of the sentence, な turns to だ or です. (です is more polite)

その花はきれいだ。（or その花はきれいです。）
– The flower is pretty.

彼女は有名だ。（or 彼女は有名です。）
– She is famous.

有名な（ゆうめいな）famous
不安な（ふあんな）anxious
静かだ（静かだ）quiet