Master Japanese Adjective Conjugations With This Handy Guide!

Adjective conjugations are a part of Japanese that can be very confusing, particularly to westerners who have never hear of such a thing. Certainly the concept is foreign, so let’s see if we can get a handle on how these conjugations work.

First off, let’s just quickly cover the two types of adjectives: -い and -な adjectives. We know the basic uses of each in that when they are used to modify nouns, we place them before nouns just like in English. For -い adjectives, we leave them as-is, and for -な adjectives, we have to use -な before the noun. Pretty straightforward, yes? But when they are being used in the predicate, they have to be dealt with in a whole different way – conjugations.

Now, let’s start with -い adjectives. Just like with verbs, we have conjugations that are non-past (present and future) and past. Within those, we conjugate to reflect negative, and we do it both formally and informally because Japanese is just that way. 

Adjectives Informal Formal
Non-Past Normal with no change Same as informal and add です to the end
Non-Past Negative Drop the – and add


Same as informal +です OR

Drop the – and add –くありませ

Past Drop the and add


Same as informal and add です to the end
Past Negative Drop the – and add


Same as informal +です OR

Drop the – and add –くありませでした


Let’s try an example using “fast”: はやい

はやい Informal Formal
Non-Past はや はやいです
Non-Past Negative はやくない はやくないです OR


Past はやかった はやかったです
Past Negative はやくなかった はやくなかったですOR



The great thing about Japanese is that there are very few irregulars. In the case of adjectives, there’s only one: “good”. We know it as いい, but it conjugates as よい. Therefore, it works like this:

いい Informal Formal
Non-Past いい いいです
Non-Past Negative よくない よくないです OR


Past よかった よかったです
Past Negative よくなかった よくなかったですOR



Now, let’s move onto -な adjectives. These are super easy in comparison to -い adjectives, as they themselves do not conjugate. Instead, we just drop the -な and add endings. I’ll make things a little less tl;dr and jump straight to an example. How about let’s use げんき? This is a good one because although it ends with an -い sound, it is not an -い adjective. I’ll explain that in a minute. For now, let’s put it to use.

Adjectives Informal Formal
Non-Past げんき げんきです
Non-Past Negative げんきじゃない OR


Past げんきだった げんきでした
Past Negative げんきじゃなかったOR




Ok, so back to the whole adjectives ending in “い” that are not -い adjectives. The simplest way I can think of to help you remember which ones are and are not -い adjectives is that the kanji for adjectives are typically two and adjectives are one kanji and some trailing hiragana ending in -い. Until you learn these kanji, it’s just something you pick up on with practice. The awesome part (/sarc) is that it is far from a hard and fast rule, but at least it’s a more-often-than-not situation. But here are some examples:

漢字 ひらがな Romaji Meaning
好き すき Suki Like, love
有名 ゆうめい Yuumei Famous
きれい きれい Kirei Pretty, beautiful
丁寧 ていねい Teinei polite
嫌い きらい Kirai to not like
便利 べんり Benri useful, convenient
元気 げんき Genki healthy
大好き だいすき Daisuki Passionate
無理 むり Muri unreasonable


Ok, so those are the basics. Now that we’ve established how we conjugate the different kinds of adjectives by dropping the final sound and adding endings, here are some other endings and how they are used. I’ll give the meaning, what ending to use, and one example each of an -い adjective and a -な adjective.


Meaning Addition Example Addition Example
Too [adj] -すぎる








Looks / seems [adj] -そう ふるそう -そう べんりそう
· Becomes -な adjective (-そう)

· いい becomes よさそう

· Adjectives ending in -ない change to -なさそう (e.g., きたない -> きたなさそう)

Become [adj] -くなる








Make into [adj] -くする








[adj] -ness -さ よわ -さ しずか
If it is [adj] -ければ ちいさければ -なれば




If it is not [adj] -くなければ おいしくなければ -でなければ びょうきでなければ
[adj] and (other adj) -くて おおきくてせがたかい -で かんたんらく
Adverb form -く はや -に げんき


Just to wrap things up, I wanted to go over the adjectives used in this guide. Obviously, there are so many adjectives that it would be impossible to include them here, but if I’m going to use examples, I should probably tell you what they are and what they mean…

漢字 ひらがな Romaji Meaning
早い はやい Hayai Fast, early
元気 げんき Genki Healthy, cheerful
暑い あつい Atsui Hot
下手 へた Heta Bad at
古い ふるい Furui Old
便利 べんり benri Useful, convenient
汚い きたない Kitanai Dirty
寒い さむい Samui Cold
好き すき Suki Likeable, to like
明るい あかるい Akarui Bright
有名 ゆうめい Yuumei Famous
弱い よわい Yowai Weak
静か しずか Shizuka Quiet, peaceful
小さい ちいさい Chiisai Small
ひま Hima Free (time)
美味しい おいしい Oishii Delicious
病気 びょうき Byouki Ill, sick
大きい おおきい Ookii Big
背が高い せがたかい Segatakai Tall (person)
簡単 かんたん Kantan Easy
らく Raku Simple


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