Lesson 10: Adjective Basics

So far we’ve gone over the case marking particles, the linking particles は・も and how to use nouns and verbs and form their negatives. Now we are going to be taking our first look into adjectives and how they work in Japanese. Broadly speaking, Japanese has two classes of words that semantically function as the equivalent of English adjectives, but function syntactically and morphologically in Japanese in two very different ways.

Useful Vocab

親切（しんせつ）・ Kind
大きい（おおきい）・ Big
綺麗（きれい）・Clean, pretty
幸い（さいわい）・ Fortunate
同じ（おなじ）・ Same
いい・ Good
格好いい（かっこういい）・Cool, handsome
やさしい・Nice, kind
新しい（あたらしい）・ New
パソコン・ PC
部屋（へや）・ Room
弟（おとうと）・ Little brother

Adjectival Nouns / “Na Adjectives”

The first type of adjective in Japanese is the “adjectival noun”, also known as “na-adjectives” and 形容動詞（けいようどうし）in Japanese. We’ve seen a couple of these so far in our vocabular examples with 好き and 嫌い. These adjectives function syntactically almost identically to nouns. When predicating a sentence, they conjugate via use of the copula だ in the same way that nouns do.

For example:

ひろしさんは学生だ・ひろしさんは学生じゃない
ひろしさんは親切だ・ひろしさんは親切じゃない

The only difference between standard nouns and adjectival nouns is that when adjectival nouns are used to directly modify another noun, they connect to the noun with な instead of the particle の, hence the often used name, “na-adjective”. This な is simply an attributive form of the copula だ.

Examples of connecting two nouns:

猫のおもちゃ (Cat toy)
自由の女神（Statue of liberty).

Examples of connecting an adjectival noun to a noun:

親切な人 (A kind person)
きれいな部屋 (A clean room)

To negate an adjectival noun, we simply negate the copula, as we learned in the previous lesson, the exact same way we learned to do with nouns:

ももこさんは親切じゃない (Momoko is not kind)
弟の部屋はきれいじゃない (My little brother’s room is not clean)

True Adjectives / “I Adjectives”

The next group of adjectives are what are variously called true adjectives, “i adjectives” or 形容詞（けいようし）in Japanese. “I-adjectives”, unlike na-adjectives, behave very much like verbs in that they can predicate sentences on their own without the use of the copula, and have their own built in system of inflection. While all Japanese verbs end in the vowel “-u”, all i-adjectives end in the hiragana い as okurigana, hence the name. Some examples of i-adjectives include 大きい、楽しい、and 新しい. Be careful though as there are some adjectives that have a hiragana い as okurigana but are actually adjectival nouns. Examples of these include 幸い and 嫌い. Some other adjectival nouns like きれい also end in a hiragana い, but when written fully in kanji (e.g. 綺麗), the い is actually part of the kanji and not an okurigana, so we can instantly tell from that that it cannot be an i-adjective.

Predicate Examples:

わたしのともだちはやさしい。 (My friend is nice)
ひろしのぱそこんはあたらしい。(Hiroshi’s laptop is new)

As you can see, the i-adjectives can end a sentence all on their own, with the copular “to be” baked into the adjective itself. It is therefore grammatically incorrect to say やさしいだ or あたらしいだ. The copula だ can only ever be used with nouns and adjectival nouns. *Never* i-adjectives.

Because of this, using i-adjectives to modify nouns directly becomes straightforward. You simply stick the adjective in front of the noun it is modifying without having to add any binding particle in the middle, like you have to do with nouns and adjectival nouns:

たけしはやさしい人だ (Takeshi is a nice friend)
大きい猫がいる (There is a big cat)

To negate an i-adjective, we simply change the final い to く and add ない：

たけしさんはやさしくない
私のコンピューターは新しくない

The reason for this is that historically, the い developed as a contraction of く＋あり, where あり was the old form of the verb ある. Most of the conjugations for i-adjectives are based on ある, in the same way that those of the copula だ are based on its uncontracted form である. So since the negative of ある is ない, the negative of i-adjectives is くない

Exception 1 – いい

The i-adjective いい meaning “good” has two forms, いい and よい, with よい being more formal. However all of its conjugations are always based on よい and not いい. So to negate, we say よくない and never いくない. This is important to keep in mind as we learn more conjugations going forward.

This also applies to adjectives that are compounds that contain いい such as かっこういい which can mean “cool” or “handsome”. The negative becomes かっこうよくない and not　かっこういくない

わたしはいい考えがある (I have a good idea)
トムさんはかっこうよくない (Tom isn’t cool)

Exception 2 – 同じ

The word 同じ (“same”) is a little weird in that it works as a sort of hybrid between i-adjectives and na-adjectives. On the one hand, it predicates sentences with the copula だ. However, it can directly modify nouns without the help of the linker な, in the same way that い adjectives can. This often doesn’t get explicitly pointed out to learners in the same way that いい is: