Japanese Adjective Usage
Japanese has two classes of adjectives that conjugate differently. 形容詞 (keiyoushi), literally "qualifying words", are often called -i or verb-like adjectives (keiyoushi is incidentally also the term used when referring to English adjectives). 形容動詞 (keiyoudoushi), literally "qualifying movement words", are often called -na or noun-like adjectives.
A third adjective category called 連体詞 (rentaishi), literally "attributive words", must always come before a noun. The category contains a mix of things that may look more like verbs (such as いわゆる), pronouns (such as あの), or -na adjectives (such as 大きな) unless you're a linguist. More importantly, they don't conjugate, so I won't mention them very often here.
There's also another category of noun-like adjectives that use たる (taru) instead of な (na) to link with nouns, and と (to) instead of に (ni) when acting as adverbs, but these -taru adjectives have mostly died out and are very rare in modern Japanese.
Arguably, none of these are properly "adjectives" in the English sense of the word, especially since -i adjectives act a lot like verbs and -na adjectives are nearly the same thing as nouns. But since they're usually used to modify nouns, "adjective" is probably the best English can do to describe them, so that's what they're generally called, and that's what I'm going with. Moving on, these adjectives can be used in several different ways.
This is when an adjective directly precedes the noun it modifies, like "cold weather" or "healthy person". -i adjectives are placed before their nouns in dictionary form; -na adjectives are the same but include the ～な (-na). Any of the conjugated short forms may also be used.
(Atarashii tokei wo kaimashita.)
"I bought a new watch."
(Hima na hito wa neru.)
"The idle person sleeps."
(Atsukunai KOOHII wo nomimasen.)
"I don't drink coffee that isn't hot."
Except in the case of rentaishi, which cannot end a sentence and must always be used attributively, this is simply a special case of sentences modifying nouns, where the sentence is just an adjective. Yes, a single word can be a complete sentence in Japanese!
On a bit of a side note, the ～な (-na) of -na adjectives is derived from the なる (naru), short for にある (ni aru), copula of classical Japanese. This is not typically relevant to modern Japanese except that ～なる is sometimes used in place of ～な for effect.
(Oroka naru ningen me...)
Also, certain classical ～なる adjectives have evolved into rentaishi (non-conjugating adjectives) in modern Japanese, but since these are fixed phrases that always contain the なる, they shouldn't cause any problems. A typical example is 単なる (tan naru).
In English, adjectives normally do not directly modify pronouns such as I, you, them, and it. Japanese has no such qualms, and is prefectly willing to attach adjectives and other descriptive phrases directly to pronouns. This, unsurprisingly, tends to complicate translation, typically resulting in either a clunky "[pronoun] that is [adjective]" phrase or, usually preferably, rewording the sentence to capture the essense more naturally.
- (from Zelda 3)
(RINKU yo, osanai omae ga taima no ken motomete oru no ka!)
"Link, one so young as you is seeking the exorcising sword!?" or more literally,
"Link, childish you are seeking the exorcising sword!?" (See? English just doesn't do it that way.)
This is where -i adjectives look a lot like verbs and -na adjectives look just like nouns. The forms mean the same thing as for verbs. To use these, simply put the noun with the appropriate adjective form in a sentence like so: [noun]は[adjective] ([noun] wa [adjective]). Alternately, put one of the short forms right before the noun, as explained above. It means the same as [noun] is/isn't/was/wasn't/etc. (depending on the form used) [adjective]. So, for example...
(Hon wa omoshiroi.)
"The book is interesting." or "Books are interesting."
(Kippu wa takaku nakatta desu.)
"The ticket was not expensive."
So here's the chart. D stands for dictionary form, and that's without the ～な for -na adjectives.
There is one exception, of a sort. The -i adjective いい (ii) is techincally a variant of よい (yoi), and conjugates as よい in all forms except nonpast affirmative. So the past affirmative casual is よくない (yokunai), the -te form is よくて (yokute), and so on.
Other than that, all adjectives conjugate regularly. Examples are included in the chart.
|-i adjectives||D + です (desu)||D|
|新しい (atarashii)||新しいです (atarashii desu)||新しい (atarashii)|
|-na adjectives||D + です (desu)||D, optionally + だ (da), or|
D + な (na) before a noun
|賑やか (nigiyaka)||賑やかです (nigiyaka desu)||賑やか(だ) (nigiyaka (da)), or|
賑やかな (nigiyaka na) [noun]
|-i adjectives||D - い + くありません (ku arimasen)
or D - い + くないです (ku nai desu)
|D - い + くない (ku nai)|
|詰らない (tsumaranai)||詰らなくありません (tsumaranaku arimasen)
or 詰らなくないです (tsumaranaku nai desu)
|-na adjectives||D + じゃありません (ja arimasen)
or D + じゃないです (ja nai desu)
|D + じゃない (ja nai)|
|きれい (kirei)||きれいじゃありません (kirei ja arimasen)
or きれいじゃないです (kirei ja nai desu)
(kirei ja nai)
|-i adjectives||D - い + かったです (katta desu)||D - い + かった (katta)|
|小さい (chiisai)||小さかったです (chiisakatta desu)||小さかった (chiisakatta)|
|-na adjectives||D + でした (deshita)||D + だった (datta)|
|元気 (genki)||元気でした (genki deshita)||元気だった (genki datta)|
|-i adjectives||D - い + くありませんでした (ku arimasen deshita)
or D - い + くなかったです (ku nakatta desu)
|D - い + くなかった|
|熱い (atsui)||熱くありませんでした (atsuku arimasen deshita)
or 熱くなかったです (atsuku nakatta desu)
|-na adjectives||D + じゃありませんでした (ja arimasen deshita)
or D + じゃなかったです (ja nakatta desu) (uncommon)
|D + じゃなかった|
|暇 (hima)||暇じゃありませんでした (hima ja arimasen deshita)
or 暇じゃなかったです (hima ja nakatta desu) (uncommon)
(hima ja nakatta)
|-i adjectives||D - い + くて (kute)|
|かわいい (kawaii)||かわいくて (kawaikute)|
|-na adjectives||D + で (de)|
|親切 (shinsetsu)||親切で (shinsetsu de)|
|-i adjectives||D - い + くなくて (ku nakute)|
|大きい (ookii)||大きくなくて (ookiku nakute)|
|-na adjectives||D + じゃなくて (ja nakute)|
|大変 (taihen)||大変じゃなくて (taihen ja nakute)|
|-i adjectives||D - い + かったら (kattara)|
|よろしい (yoroshii)||よろしかったら (yoroshikattara)|
|-na adjectives||D + だったら (dattara)|
|馬鹿 (baka)||馬鹿だったら (baka dattara)|
|-i adjectives||D - い + くなかったら (ku nakattara)|
|いい (ii)||よくなかったら (yoku nakattara)|
|-na adjectives||D + じゃなかったら (ja nakattara)|
|愚か (oroka)||愚かじゃなかったら (oroka ja nakattara)|
|-i adjectives||D - い + ければ (kereba); D + なら (nara) is similar|
|面白い (omoshiroi)||面白ければ (omoshirokereba); 面白いなら (omoshiroi nara) is similar|
|-na adjectives||D + であれば (de areba); D + なら (nara) is similar|
|素直 (sunao)||素直であれば (sunao de areba); 素直なら (sunao nara) is similar||Negative
|-i adjectives||D - い + くなければ (ku nakereba); D - い + くないなら (ku nai nara) is similar|
|古い (furui)||古くなければ (furuku nakereba); 古くないなら (furuku nai nara) is similar|
|-na adjectives||D + じゃなければ (ja nakereba); D + じゃないなら (ja nai nara) is similar|
|変 (hen)||変じゃなければ (hen ja nakereba); 変じゃないなら (hen ja nai nara) is similar|
|Alternative||Any||the appropriate past tense + り (ri)|
|長い (nagai)||長かったり (nagakattari) if positive|
|長くなかったり (nagaku nakattari) if negative|
|鮮やか (azayaka)||鮮やかだったり (azayaka dattari) if positive|
|鮮やかじゃなかったり (azayaka ja nakattari) if negative|
Note that many of these forms, particularly for -na adjectives, end in a form of the copula. Where appropriate, other variants of the copula may be substituted, such as である (de aru) instead of です (desu).
Also keep in mind that an adjective can end in い (i) and still be a -na adjective rather than an -i adjective. The standard example is きれい (kirei), which can also be written in kanji as 奇麗, though it generally isn't due to the complexity of the characters. Note that the い is part of the kanji and not a trailing character, as it is in -i adjectives like 黒い (kuroi), for example.
Adjectives also have highly formal variants. For -na adjectives, this is simple; just use the highly polite copula, でございます (de gozaimasu) instead of the usual です (desu). For -i adjectives, it's more complicated.
|a as the vowel in the next to last kana||change final ai to ou and add ございます (gozaimasu)|
|i as the vowel in the next to last kana||change final ii to yuu and add ございます (gozaimasu)|
|u as the vowel in the next to last kana||change final ui to uu and add ございます (gozaimasu)|
|o as the vowel in the next to last kana||change final oi to ou and add ございます (gozaimasu)|
|早い (hayai)||早うございます (hayou gozaimasu)|
|かわいい (kawaii)||かわゆうございます (kawayuu gozaimasu)|
|嬉しい (ureshii)||嬉しゅうございます (ureshuu gozaimasu)|
|大きい (ookii)||大きゅうございます (ookyuu gozaimasu)|
|眠い (nemui)||眠うございます (nemuu gozaimasu)|
|遅い (osoi)||遅うございます (osou gozaimasu)|
These may also be preceded with the honorific お (o). Certain idiomatic phrases come from this form, such as お早うございます (ohayou gozaimasu), which functions as "good morning" but is literally just "it is early" phrased very politely.
Seems... Looks like... (-sou ending)
To say how something seems, drop the final ～い (-i) for -i adjectives, leave out the ～な (-na) for -na adjectives, and add ～そう (-sou) to what's left. The result acts as a -na adjective. It indicates that whatever you are referring to seems to be or looks like the adjective you started with, when you don't have enough information to be sure. As such, ～そう is rarely used with adjectives such as "pretty" that depend on perception, since it's difficult to imagine a situation in which you could tell that something seems to be pretty without being able to say that it actually is pretty.
When using ～そう with negatives, create the negative form as usual, then change the final ～ない (-nai) to ～なさそう (-nasasou).
Finally, for whatever reason, いい (ii) becomes よさそう (yosasou), not the more plausible いそう (isou) or よそう (yosou).
(Kono SUPOUTSU wa kantansou.)
"This sport seems simple."
(Sore wa atatakasou na SEETAA.)
"That's a warm-looking sweater."
(Omoshiroku nasasou desu.)
"It does not appear to be interesting."
Also refer to the related clause endings みたい (mitai) and よう (you).
The adverbial form—add に (ni) as explained in the "as other parts of speech" section below—of this occurs fairly often with certain adjectives and may be used in ways that are not intuitive to English speakers, or at least don't translate cleanly.
(oishisou ni RAAMEN wo taberu)
"eats ramen in a way that suggests that it's delicious"
"Eats hungrily" is a reasonable approximation in this particular case.
Seems... Feels like... (-ge ending)
For another way to say how something seems, drop the final ～い (-i) for -i adjectives, and add ～げ (-ge). The result acts as a -na adjective. It indicates that whatever you are referring to seems to be the adjective you started with, or that you have a feeling that it is.
(nani ka iitage na kao)
"a face that gives me the feeling he wants to say something"
(kanashige ni aruku)
"walk with an air of sadness"
～げ seems to get less use than the similar ～そう (-sou) ending. As far as meaning goes, ～そう tends to suggest a basis in specific observable evidence, while ～げ (which comes from the kanji 気) tends to have a more intuitive or emotional aspect.
While ～げ can go with the ～たい (-tai) verb ending, as shown in the example above, it rarely does so for verbs other than 言う (iu, to say), also featured in the example.
Observations about other people (-garu) and (-gatte iru)
Some adjectives, such as かわいい (kawaii, roughly translating to cute) can be used as-is when describing other people, but others refer to things such as personal feelings that an outside observer can never be quite sure of. Adjectives of this type include 嬉しい (ureshii, happy), 痛い (itai, painful), and the ～たい (-tai) verb ending, which indicates a desire. To talk about other people, the tendency is to be more indirect, perhaps by saying that they said they want to, or that you think they want to. Another way, for -i adjectives of this type, is to drop the final い and add ～がる (-garu). This ending conjugates as a regular godan (-u) verb, and indicates that your observations of the person point toward this conclusion, or, since the person in question acts as the subject, that this person shows evidence of feeling this way.
For example, feeling fear is 怖い (kowai), while showing fear is 怖がる (kowagaru).
The adjective 欲しい (hoshii), meaing wanted or wished for, often acts like this and is normally used as [object]が欲しい ([object] ga hoshii). However, when making an observation of want with ～がっている, use を (wo) instead of が (ga).
(MEARII wa kanashigatte iru.)
"Mary seems sad" (based on how she's acting or other outward indications).
(TOMU san wa tomodachi wo hoshigaimasu.)
"Tom strikes me as someone who wants a friend."
Several other adjectives also use the ～がる suffix so often that you're likely to find the combined form listed as its own dictionary entry. For instance, 可愛い (kawaii), one sense of which is to feel affectionate about someone, forms the verb 可愛がる (kawaigaru), which refers more specifically to demonstrating that affection. A perhaps more interesting one is 強がる (tsuyogaru), from the adjective 強い (tsuyoi, strong). Whether because strength shouldn't be too hard to observe already or just because people so often do this, 強がる means to make a deliberate effort to appear strong, often despite actually lacking that strength.
With more immediacy:
～がる frequently appears in the progressive form ～がっている (-gatte iru). Since this indicates an action in progress, it means that the person in question is currently displaying whatever evidence suggests these feelings. Let's use 欲しい to demonstrate.
(DII ESU ga hoshii)
"I want a DS." (since I used the direct form, I'm almost certainly talking about my own wants)
(Konata ga DII ESU wo hoshigaru.)
"Konata shows signs of wanting a DS." (approrpate if she gushes about it at great length, but isn't necessarily currently doing so)
(Konata ga DII ESU wo hoshigatte iru.)
"Konata is showing signs of wanting a DS." (appropriate if she's staring at a window display and drooling right now)
Too Much (-sugiru)
To express the idea of "too much", add the auxiliary verb ～すぎる (-sugiru). For -i adjectives, first drop the final ～い (-i); for -na adjectives, just leave out the ～な (-na). The ～すぎる ending conjugates as an ichidan (-ru) verb.
Referring to someone or something with adjective + すぎる has a negative connotation. You wouldn't normally, for example, say that someone is 楽しすぎる (tanoshisugiru, too much fun), unless you're suggesting that this is a bad thing in some way, such as being so much fun that you didn't get any sleep all weekend and now you're dead on your feet.
(Kono tokei wa furusugimasu.)
"This clock is too old."
(Shizukasugiru n da...)
"It's too quiet..."
To moderate an -i adjective, similar to using the English ending "-ish", replace the final ～い (-i) with ～め (-me) and use the result as a -na adjective. As usual, the adverbial form also applies. This usage might apply only to certain adjectives, and there doesn't seem to be an equivalent for -na adjectives at all.
(ookime na SHATSU)
(Hayame ni tsuita.)
"We arrived a bit on the early side."
As Other Parts of Speech
-i adjectives can be used as abstract nouns by replacing the ending ～い (-i) with ～さ (-sa), though this doesn't apply to all adjectives. The resulting noun refers to the attribute that the adjective describes.
You can do the same with some -na adjectives by adding ～さ (-sa), but this seems to be somwhat less common.
(Nan to iu orokasa da.)
-na adjectives are sometimes used directly as nouns, especially in colloquial speech, though perhaps they technically shouldn't be.
(Hottoke, kono BAKA.)
"Leave me alone, you idiot."
All adjectives have a corresponding adverbial form. -i adjectives change the final ～い (-i) to ～く (-ku), while -na adjectives add に (ni).
(shizuka ni hanasu)
As noted in the introduction, -taru adjectives use と (to) instead of に (ni).
Adjectives can be used as verbs with a few changes. Make the adverbial form (above) and add なる (naru) to mean "become [adjective]", or する (suru) to mean "make [adjective]".
(Mise ga isogashiku natta.)
"The store got busy." or "The store got busier."
(Sensei ga shiken wo kantan ni shite kureru.)
"The teacher will make the test easy." or "The teacher will make the test easier."
Notice that there's no way to tell a relative change (becoming more than it was before) from an absolute one (wasn't before but is now). Looking the first example above, if the change is absolute, then the store had not been busy before, but now is. If the change is relative, then the store may or may not have been busy at first, but is now more busy than it had been. In other words, 忙しくなった (isogashiku natta) could mean either "get busy" or "get busier". The intended meaning can be clarified by context, and there are several simple ways to make the type of change explicit.
(Shizuka datta mise ga isogashiku natta.)
"The store that had been quiet became busy."
(Mise ga motto isogashiku natta.)
"The store became more busy."
(Mise ga sara ni isogashiku natta.)
"The store became further busy."
(Mise ga mae yori isogashiku natta.)
"The store became busier than [it was] before."
より (yori) by itself also works, though that leaves some ambiguity as to what it's more than. Then again, English "busier" (to keep the same example) has the same ambiguity, and how often does anyone care?
Additionally, -na adjectives such as 好き (suki) that seem more or less like verbs are sometimes directly used as verbs in colloquial speech, even though this isn't considered correct usage.
(shuumatsu wo suki.)
"I like weekends."
For what it's worth, the proper usage is 週末が好き (shuumatsu ga suki), with "weekend" marked as the subject.