There are two types of adjectives in Japanese: i-adjectives and na-adjectives. The type of adjective is determined by its ending or—more precisely—the grammar that is required to join the adjective to nouns or transform the adjective into an adverb. Fortunately, it is obvious in almost all cases when looking at a new adjective whether it is an i-adjective or a na-adjective so you aren’t faced with the challenge of rote learning groups.
Here I’ll introduce i-adjectives and na-adjectives and their respective conjugations—yes, adjectives conjugate in Japanese! In English, adjectives themselves don’t transform when we talk in the negative, past, or past negative tense. In other words, in the following sentences the word “expensive” does not change.
The shoes are expensive. |
The shoes are not expensive. |
The shoes were expensive. |
The shoes were not expensive. |
The other thing you might notice is that some adjectives in Japanese are not adjectives in English. For instance, the most common way of saying “to like” uses “like” as an adjective.
I-Adjectives
All i-adjectives end in い which is written in hiragana. Below is a selection of JLPT N5 i-adjectives.
English | Japanese |
Good | いい |
Cheap | |
Kind | |
Light | |
New | |
Busy | |
Big | |
Interesting | |
Fun, enjoyable | |
Old |
The conjugation for i-adjectives always follows the same rules with just one exception: the adjective “good” (いい). Here you only have to remember that when the adjective conjugates into the past, negative, or past negative the first syllable becomes よ.
In fact, よい is the archaic word for good. It is still used today in formal writing but rarely in conversation in this standard form.
The other critical grammatical point to note is that we cannot add the standard form of the auxiliary verb to i-adjectives (this is the one exception to rule that all sentences must end with a verb in Japanese). For example, “this is cheap”:
これは |
これは |
Negative & Past Negative
For the negative and past negative we change the い to a く and then add the standard conjugation of the verb ある (the verb “to exist” for inanimate objects) which we met earlier.
English | Dictionary | Negative | Past Negative |
to exist | ある | ない | なかった |
For example, to say “not expensive”:
English | Dictionary | Negative | Past Negative |
Cheap | |||
Big |
Past Tense
For all other i-adjectives you simply change the final い to かった. Take the adjective for “tall” or “expensive” (たかい), for example:
For the adjective “good” the past conjugation becomes:
いい → よかった
Polite Conjugations
For the polite conjugation we follow exactly the same rules as above, but add the polite form of the auxiliary verb: です.
Standard | Polite |
いい | いいです |
Good | Good |
Standard | Polite |
よかった | よかったです |
Was good | Was good |
Standard | Polite |
よくない | よくないです |
Is not good | Is not good |
Standard | Polite |
よくなかった | よくなかったです |
Was not good | Was not good |
For the negative and past negative we can also use the polite conjugation for ある instead.
English | Polite Present | Polite Negative | Polite Past Negative |
to exist | あります | ありません | ありませんでした |
Polite I | Polite II |
よくないです | よくありません |
Is not good | Is not good |
Polite I | Polite II |
よくなかったです | よくありませんでした |
Was not good | Was not good |
Both ways of conjugating to the negative and past negative are used in Japanese; however, the latter is arguably more polite.
Na-Adjectives
Na-adjectives can be conveniently defined as all those that don’t end with い with just a few exceptions. The exceptions are “beautiful” (きれい), “hate” (きらい), and “grateful/happy” (さいわい) which look like い adjectives, but in fact conjugate as na-adjectives. Below is a selection of JLPT N5 na-adjectives.
English | Japanese |
Like | |
Famous | |
Quiet | |
Convenient | |
Important, precious | |
Skilful, good at | |
Unskilful, not good at | |
Necessary | |
Splendid | |
Serious | まじめ |
Grammatically speaking, we must append the auxiliary verb to na-adjectives; however, in casual conversation this will very often be omitted.
I like (it). |
I hate (it). |
Because na-adjectives take the auxiliary verb we already know their conjugation. We just need to conjugate the auxiliary verb to get the negative, past, or past negative for both the standard and polite forms.
Tense | Standard | Polite |
Present | ||
Past | ||
Negative | ||
Past Negative |
I didn’t like (it). |
And, as we’ve seen before, in both cases we can replace では with the more colloquial じゃ.
I didn’t like (it). |