Adjectives are important in language learning. They are used to describe things and express how you feel about something. It’s like saxing “the shoes are beautiful” or “the meal was expensive”

In Japanese, adjectives are classified into two categories: i-adjectives and na-adjectives. How they’re classified is based on the ending of the adjective. Depending on the type of adjective it is, you conjugate it differently. Conjugation is a huge part of Japanese language and grammar.

But don’t worry, all adjectives fall in either one of these two categories. We’ll look at conjugating into negative, past and past negative tenses. Once you have gotten the hang of these conjugations, you’ll be a pro in Japanese adjectives. 

I-Adjectives

I-adjectives refer to adjectives that end with the い hiragana. Here are some examples of the i-adjective:

Good – いい (ii)

Cheap –安い (yasui)

Big – 大きい (ookii)

New – 新しい (atarashii)

Fun –  楽しい (tanoshii)

Interesting – 面白い (omoshiroi)

If you notice, they all end with the same hiragana い. Almost all i-adjectives conjugate the same, except for one: いい (good) changes its first syllable to よい to other tenses.

One thing to note is that i-adjectives cannot have the auxiliary verb added. For example, you cannot say it as “これは大きい”, but instead say it as “これは大きい”. 

Past Tense

Changing an i-adjective to its past tense is pretty simple. All you have to do is change the ending い to かった. 

(I-adjective without い) + かった

Here are some examples of the conjugation:

Is Expensive – 高い (takai) 

Was expensive – 高かった (takakatta)

Is cheap – 安い (yasui)

Was cheap – 安かった (yasukatta)

Is big – 大きい (ookii) 

Was big – 大きかった (ookikatta)

Interesting – 面白い (omoshiroi) 

Was interesting – 面白かった (omoshirokatta)

The only exception is いい (ii) , which changes to よかった (yokatta).

Negation

To make an i-adjective its negation, you have to change the ending い to く. Then, you add nai (ない), which is the negation of the word “aru” (ある, to exist). 

(I-adjective without い) + く + ない

For example, let’s use the word “expensive (高い)” and change it to its negation.

Not expensive =  高 + く + ない = 高くない

Here are some other conjugations to the negative form of an adjective:

Cheap – 安い (yasui) 

Not cheap – 安くない (yasukunai)

Big – 大きい (ookii) 

Not big – 大きくない (ookinunai)

Interesting – 面白い (omoshiroi) 

Not interesting – 面白くない (omoshirokunai)

Negative Past Tense

If you want a negative past tense, you first negate the word, then change it to its past tense. The formats is:

Negative i-adjective (without い) + かった

For example, let’s change “expensive” to its past negative.

Was not expensive = 高 + く + な (ない without the い) + かった = 高くなかった

Here are some other examples:

Cheap – 安い (yasui) 

Was not cheap – 安くなかった (yasukunakatta)

Big – 大きい (ookii) 

Was not big – 大きくなかった (ookinunakatta)

Interesting – 面白い (omoshiroi) 

Was not interesting – 面白くなかった (omoshirokunakatta)

Polite Conjugation

To make the adjective polite, you add desu (です) after the i-adjective, regardless of tense.

I-adjective + です

Here’s an example in various tenses:

Present: Cheap – 安いです (yasui desu) 

Past: Was cheap – 安かったです (yasukatta desu)

Negative: Not cheap – 安くないです (yasukunai desu)

Past Negative: Was not cheap – 安くなかったです (yasukunakatta desu)

Alternatively, you can change the negative form and past negative form into a different way of polite form. 

ないです = ありません

なかったです = ありませんでした

Here are some examples: 

Negative: 

Not cheap – 安くないです (yasukunai desu) = 安くありません (yasuku arimasen)

Past Negative: 

Was not cheap – 安くなかったです (yasukunakatta desu) = 安くありませんでした (yasuku arimasen deshita)

Na-Adjectives

Na-adjectives are adjectives that end with な. It’s easier to look at it as those that don’t end with い. Here are some examples of na-adjectives:

Quiet – 静か (shizuka)

Like  – 好き (suki)

Convenient – 便利 (benri)

Good at – 上手 (jouzu)

However, there are some exceptions to the rule. For example, the word “beautiful’ (綺麗, きれい), “hate” (嫌い, きらい) and “grateful” (幸い, さいわい) all end with い, but they are actually na-adjectives.

Unlike i-adjectives, the auxiliary verb is supposed to be added to na-adjectives, but casually can be omitted. For example, to say “it’s quiet”, you say it with a “da” at the end: “静か” (shizuka da).

Past Tense & Polite Past Tense

Because na-adjectives take on the auxiliary verb, it’s easier for the conjugation. This is similar to noun conjugations where you just add “datta” (だった) or “deshita” (でした) for its past tense.

Na-adjective + だった (informal) / でした (formal)

Here are some examples:

Is quiet – 静か (shizuka)

Was quiet – 静かだった (shizuka datta) / 静かでした (shizuka deshita)

Like  – 好き (suki)

Liked – 好きだった (suki datta) / 好きでした (suki deshita)

Convenient – 便利 (benri)

Was convenient – 便利だった (benri datta) / 便利でした (benri deshita)

Is good at – 上手 (jouzu)

Was good at – 上手だった (jouzu datta) / 上手でした (jouzu deshita)

Negation & Polite Negation

Similarly to the past tense, it’s pretty simple to conjugate to its negation, past negation, and polite negation. They conjugat similarly to nouns.

Let’s look at negation first. You add “de ha nai” (ではない) or “de ha arimasen” )ではありません: 

Na-adjective + ではない (informal) / ではありません (formal)

Here’s an example:

Quiet – 静か (shizuka)

Not quiet – 静かではない (shizuka de ha nai) / 静かではありません (shizuka de ha arimasen)

Past Negation & Polite Past Negation

For the past negation, you add “de ha na katta” (ではなかった) or “de ha arimasen deshita” (ではありませんでした) to the adjective:

Na-adjective + ではなかった (informal) / ではありませんでした (formal)

Here’s an example: 

Quiet – 静か (shizuka)

Not quiet – 静かではなかった (shizuka de ha na katta) / 静かではありませんでした (shizuka de ha arimasen deshita)

Conjugate Adjectives Like A Pro!

And that’s a comprehensive guide to basic adjectives and it’s conjugations into various tenses! If you like this kind of article, you should check out our Nihongo Master Podcast as we have a language series, Study Saturday, where we break down Japanese grammar similar to this one!