All About Japanese Adjectives

There are two distinct types of adjectives in Japanese: i-adjectives and na-adjectives. I-adjectives all end in "~ i," though they never end in "~ ei" (e.g. "kirei" is not considered an i-adjective.)

Japanese adjectives differ significantly from their English counterparts (and from their counterparts in other Western languages). Although Japanese adjectives have functions to modify nouns like English adjectives, they also function as verbs when used as predicates.

This is a concept that will take some getting used to.

For example, "takai（高い）" in the sentence "takai kuruma （高い車）" means, "expensive". "Takai（高い）" of "kono kuruma wa takai （この車は高い）" means not just "expensive" but "is expensive".

When i-adjectives are used as predicates, they may be followed by "~ desu（～です）" to indicate a formal style. "Takai desu （高いです）" also means, "is expensive" but it is more formal than "takai （高い）".

Here are lists of common i-adjectives and na-adjectives.

Common I-Adjectives

Common Na-Adjectives

Modifying Nouns

When used as modifiers of nouns, both i-adjectives and na-adjectives take the basic form, and precede nouns just like in English.

I-Adjectives as Predicates

As mentioned above, adjectives in Japanese can function like verbs. Therefore, they conjugate just like verbs (but probably much more simply). This concept can be confusing for first-time students of the Japanese language. 

Informal

Present Negative: Replace the final ~ i with ~ ku nai

Past: Replace the final ~ i with ~ katta

Past Negative: Replace the final ~ i with ~ ku nakatta

Formal

Add ~desu to all of the informal forms.

There is also a variation in the formal negative forms.
* Negative: Replace ~i with ~ku arimasen
* Past Negative: Add ~ deshita to ~ku arimasen 
These negative forms are considered slightly more polite than others.

Here is how the adjective "takai (expensive)" is conjugated.

There is only one exception to the rule of i-adjectives, which is "ii (good)". "Ii" derives from "yoi," and its conjugation is mostly based on "yoi".

Na-Adjectives as Predicates

These are called na-adjectives because "~ na" marks this group of adjectives when directly modifying nouns (e.g. yuumeina gaka). Unlike i-adjectives, na-adjectives cannot be used as predicates themselves. When a na-adjective is used as a predicate, the final "na" is deleted and followed by either "~ da" or "~ desu (in formal speech)". As with nouns, "~ da" or "~ desu" changes the word's form to express the past tense, the negative and the affirmative.