Why do I write “adjectives” in quotes for this chapter? Because your mind has a preset idea of what an adjective is—based on how English uses words called adjectives to modify nouns—and the Japanese adjective is not quite the same. It is indeed a class of words that modifies nouns, but it does so in a different way than the corresponding class in English. Hence, your intuition will be wrong in some cases. The best way to begin to understand this idea is just to plunge in.
Two Kinds of Adjectives
There are two classes of objects that act as what we call adjectives in English. They are classed as -i adjectives and -na adjectives. The first group are genuine Japanese words and the second are foreign words that got incorporated into the language (mostly Chinese, but the really new ones might be English, German, or French).
In Japanese, adjectives may act differently when used to modify nouns (“the green table”) vs. when used as predicates (“the table is green”), so these cases are separated.
In -na adjectives, the -na ending is used when the adjective modifies a noun, but not when it’s used as a predicate. The past and negative cases are formed as they usually are in Japanese. Thus:
Kireina kimono (pretty kimono)
Kimono wa kirei desu ([your] kimono is pretty)
Kimono wa kirei dewa arimasen or
Kimono wa kirei ja nai desu ([your] kimono is not pretty)
Kimono wa kirei deshita ([your] kimono was pretty)
Kimono wa kirei dewa arimasendeshita or
Kimono wa kirei ja nakatta desu ([your] kimono was not pretty)
(Ja is a contraction of dewa, and is generally more casual, so you would be more likely to use these forms in speech. Nai is the plain-form [familiar/casual] present tense of arimasen and nakatta is the corresponding past-tense form for arimasendeshita. Don’t sweat all these differences too much—you’ll learn from context which form to use when).
But perhaps a clearer way to think of this is that -na is a form of the copula da (the casual form of desu).
Kirei da (it is pretty)
Kirei na yama (a pretty mountain)
Yama ga kirei da (the mountains are pretty)
Yama ga kirei na kuni (a country where the mountains are pretty)
These examples hark forward to the section below called Hard-to-Understand Modifiers. After you’ve read that, and have a sense for how you stack up adjective phrases in front of nouns, come back and read this part about –na being a form of da, and it will make sense.
[If you want to be even more advanced, you can think about how no serves the same purpose as -na for noun modifiers. For example, Tomodachi ga nihonjin da means “Their friends are Japanese,” and Tomodachi ga nihonjin no gakusei means “students whose friends are Japanese”). See?]
-I adjectives are different. These are sometimes called “adjective verbs” because they seem to blend the properties of adjectives and verbs. This is seen in the fact that the negative forms incorporate the adverbial ending -ku.
An example of an -i adjective is oishii (“tasty” or “delicious”). The “root” adjective is oishi, and the -i ending is used since it’s an -i adjective. (Note that not all adjectives ending in “i” are -i adjectives. See kirei above).
-i adjectives work like this:
Oishii sushi (delicious sushi)
Sushi wa oishii desu (the sushi is delicious)
Sushi wa oishikunai desu or Sushi wa oishiku arimasen (the sushi is not delicious)
Sushi wa oishikatta desu (the sushi was delicious)
Sushi wa oishikunakatta desu or Sushi wa oishiku arimasendeshita (the sushi was not delicious)
In this case, there is no change in ending when the adjective is used as a noun modifier vs. as a predicate. But the conjugation of the “verb” is actually the conjugation of the adjective! Desu is present-tense positive, but it can be used for all four of the above cases. (You can also use arimasen; again, don’t sweat the differences too much. But even if conjugating arimasu, you still change to the “adverb” ending on oishii).
Changing the adjective form is completely logical; there are no weird exceptions. To negate, remove the final -i and add -kunai; for past tense, add -katta; and for negative past, add -kunakatta. (Technically, in the negation cases, you are adding -ku plus an extra word, either nai or nakatta. That’s because the -ku form is the adverbial form of the adjective (like adding “ly” in English), and you are really using this form when you negate. But that’s another story. Adverbs aren’t quite like they are in English either!)
So really, a better translation for the word oishii than “delicious” is “is delicious.” Then it makes sense that oishikunai means “is not delicious.” See? The adjective contains the verb.
If this seems confusing, imagine that it’s a little bit like the way we have a natural tendency to begin understanding a foreign language by translating the words we hear. We hear a sentence, play it through some translator in our head, get the English version, and finally understand it. There is a fabulous “click” moment when studying a foreign language where you realize that you are no longer translating. You are just understanding the language as itself. It’s such a great feeling to get to that point.
Now apply that same concept to grammar, not just the meaning of the words. Japanese is not an Indo-European language, but still, we have to start by “translating” the grammar into English grammatical concepts in order to understand what’s going on. We have to think about verbs and adjectives in a similar way as we do in English. Someday you will “click” into Japanese grammar and suddenly find that you are understanding the parts of speech as they are in Japanese, not using English grammar as a clumsy intermediary.
OK, so we’ve gone over how you use “adjectives” to directly modify nouns. This is, however, only the simplest way to use an adjective.
There are also adjectival phrases and clauses. In English, these are structures set off by the words “that,” “which,” and “who.” Examples include “the letter that you sent me,” and “the book I wrote” [sometimes we drop the “that”, a tendency that must be confusing to foreigners!]. Each of the final phrases is modifying the noun that comes before it.
In Japanese, there is no word for “that,” “which,” or “who” in the sense used above. Modifying phrases of this type are crunched together into a giant “adjective” that comes before the noun just like a simpler adjective.
So “the letter that you sent me” becomes “the you-sent-me letter”:
watashi ni okutta tegami (tegami is “letter”; it is modified by the phrase watashi ni okutta, “sent-to-me”).
“The book I wrote” becomes “the I-wrote book”:
watashi ga kaita hon
Ga marks watashi as the grammatical subject of the modifying clause. If the clause is short, you can also use the particle no to mark the subject (historically, ga and no are the same particle, which I find puzzling). Note that you can never use no to mark the subject of a normal declarative sentence. Also, you would tend not to use wa (the topic marker) within a clause; that doesn’t fit with wa‘s grammatical meaning. (More on wa and ga in the Particle chapter. This is a tricky issue).
While this adjectival structure makes logical sense, and is pretty easy to read or write, I find that it is nearly impossible to hear correctly, even when the modifying phrase is only moderately long. Check this out:
Ano mise wa senshuu imouto no tanjoubi ni puresento o katta toki kaban o nusumareta mise desu yo.
Everything between wa and the second mise is a gigantic adjective. It means, “That is the store where I had my bag stolen last week when I was buying a birthday gift for my younger sister.” These sorts of constructions are hard to hear on the fly.