Part1: I-Adjectives and Na-Adjectives

There are two 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 an i-adjective.)

Japanese adjectives differ from their English counterparts. Although Japanese adjectives have functions to modify nouns like English adjectives, they also function as verbs when used as predicates. 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

atarashii 新しい	new	furui 古い	old
atatakai 暖かい	warm	suzushii 涼しい	cool
atsui 暑い	hot	samui 寒い	cold
oishii おいしい	delicious	mazui まずい	bad tasting
ookii 大きい	big	chiisai 小さい	small
osoi 遅い	late, slow	hayai 早い	early, quick
omoshiroi 面白い	interesting, funny	tsumaranai つまらない	boring
kurai 暗い	dark	akarui 明るい	bright
chikai 近い	near	tooi 遠い	far
nagai 長い	long	mijikai 短い	short
muzukashii 難しい	difficult	yasashii 優しい	easy
ii いい	good	warui 悪い	bad
takai 高い	tall, expensive	hikui 低い	low
yasui 安い	cheap	wakai 若い	young
isogashii 忙しい	busy	urusai うるさい	noisy

Common Na-Adjectives

ijiwaruna 意地悪な	mean	shinsetsuna 親切な	kind
kiraina 嫌いな	distasteful	sukina 好きな	favorite
shizukana 静かな	quiet	nigiyakana にぎやかな	lively
kikenna 危険な	dangerous	anzenna 安全な	safe
benrina 便利な	convenient	fubenna 不便な	inconvenient
kireina きれいな	pretty	genkina 元気な	healthy, well
jouzuna 上手な	skillful	yuumeina 有名な	famous
teineina 丁寧な	polite	shoujikina 正直な	honest
gankona 頑固な	stubborn	hadena 派手な	showy

Part 2: The Use of 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	chiisai inu 小さい犬	small dog
	takai tokei 高い時計	expensive watch
Na-Adjectives	yuumeina gaka 有名な画家	famous painter
	sukina eiga 好きな映画	favorite movie

I-Adjectives as Predicates

As mentioned before, adjectives can function like verbs. Therefore, they conjugate just like verbs (but probably much more simply).

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.

	Informal	Formal
Present	takai 高い	takai desu 高いです
Present Negative	takaku nai 高くない	takaku nai desu 高くないです takaku arimasen 高くありません
Past	takakatta 高かった	takakatta desu 高かったです
Past Negative	takaku nakatta 高くなかった	takaku nakatta desu 高くなかったです takaku arimasen deshita 高くありませんでした

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".

	Informal	Formal
Present	ii いい	ii desu いいです
Present Negative	yoku nai 良くない	yoku nai desu 良くないです yoku arimasen 良くありません
Past	yokatta 良かった	yokatta desu 良かったです
Past negative	yoku nakatta 良くなかった	yoku nakatta desu 良くなかったです yoku arimasen deshita 良くありませんでした

Na-Adjectives as Predicates

They are called na-adjectives because "~ na" marks this group of adjectives when directly modifying noun (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 its form to express the past tense, the negative, and the affirmative.

	Informal	Formal
Present	yuumei da 有名だ	yuumei desu 有名です
Present Negative	yuumei dewa nai 有名ではない	yuumei dewa arimasen 有名ではありません
Past	yuumei datta 有名だった	yuumei deshita 有名でした
Past negative	yuumei dewa nakatta 有名ではなかった	yuumei dewa arimasen deshita 有名ではありませんでした