い-Adjectives (i-adjectives)
Learning Objectives
- Identify い-Adjectives by their ending.
- Conjugate い-Adjectives into Present Negative, Past, and Past Negative forms.
- Use adjectives to modify nouns directly.
- Master the irregular adjective いい (Good).
In English, adjectives are simple words that attach to nouns (“a cold drink”) or follow the ‘to be’ verb (“The drink is cold”). If you want to change the tense to the past, you change the verb (“The drink was cold”).
In Japanese, however, there is a special group of adjectives that act almost like verbs! They are called い-Adjectives (i-adjectives) because they always end with the Hiragana character い (i). Instead of relying on the copula (です/でした) to show tense or negativity, the adjective itself changes its ending! Let’s learn how to bend these magical words.
1. Present Affirmative: “It is [Adjective]”
To say that something currently holds a quality, leave the adjective exactly as it is (with its final い intact) and add です (desu) to make it polite.
[!CAUTION] Remember, in Polite Speech, you still add です. But the です here is just acting as a “politeness marker”, not doing the actual grammatical heavy lifting! In casual speech, you simply drop the です entirely. (e.g., さむい！ “It’s cold!“)
きょう は さむい です。
Kyou wa samui desu.
Today is cold.
この くるま は たかい です。
Kono kuruma wa takai desu.
This car is expensive.
にほんご は おもしろい です。
Nihongo wa omoshiroi desu.
Japanese is interesting.
2. Present Negative: “It is NOT [Adjective]”
Here is where the magic starts! To make an い-adjective negative, you drop the final い and replace it with くない (ku nai). Then, add です to remain polite.
Example: さむい (Cold) ➔ さむくない (Not cold).
きょう は さむくない です。
Kyou wa samukunai desu.
Today is not cold.
この ほん は たかくない です。
Kono hon wa takakunai desu.
This book is not expensive.
えいが は おもしろくない です。
Eiga wa omoshirokunai desu.
The movie is not interesting.
[!NOTE] In extremely formal or textbook Japanese, you might see くありません (ku arimasen) instead of くない です (kunai desu). Both are grammatically correct and mean the same thing, but くない です is far more common in modern everyday speech.
3. Past Affirmative: “It WAS [Adjective]”
Do not use でした! Because い-adjectives conjugate themselves, you show the past tense by dropping the final い and replacing it with かった (katta). Then, add です for politeness.
Example: さむい (Cold) ➔ さむかった (Was cold).
きのう は さむかった です。
Kinou wa samukatta desu.
Yesterday was cold.
テスト は むずかしかった です。
Tesuto wa muzukashikatta desu.
The test was difficult.
ケーキ は おいしかった です。
Kēki wa oishikatta desu.
The cake was delicious.
4. Past Negative: “It was NOT [Adjective]”
This form combines the Negative (く) and the Past (かった). You drop the final い and replace it with くなかった (ku nakatta).
Example: さむい (Cold) ➔ さむくなかった (Was not cold).
きのう は さむくなかった です。
Kinou wa samukunakatta desu.
Yesterday was not cold.
テスト は むずかしくなかった です。
Tesuto wa muzukashikunakatta desu.
The test was not difficult.
パーティー は おもしろくなかった です。
Pātī wa omoshirokunakatta desu.
The party was not fun/interesting.
5. Direct Noun Modification: “A [Adjective] [Noun]”
Just like English, you can place an adjective directly in front of a noun to describe it (e.g., “A cold day”). For い-adjectives, it is incredibly simple: just leave the い attached!
たかい くるま を かいました。
Takai kuruma o kaimashita.
I bought an expensive car.
おいしい みず を のみます。
Oishii mizu o nomimasu.
I drink delicious water.
さむい ひ
Samui hi
A cold day
6. The Exception: いい (Good)
There is exactly one irregular い-adjective you must memorize: いい (ii), meaning “good”. Historically, this word was pronounced よい (yoi). In modern Japanese, we say “いい” for the present affirmative, but for all other conjugations, it reverts back to its “よい” root!
- Present Affirmative: いい です (ii desu) - It is good.
- Present Negative: よくない です (yo-kunai desu) - It is not good.
- Past Affirmative: よかった です (yo-katta desu) - It was good.
- Past Negative: よくなかった です (yo-kunakatta desu) - It was not good.
Common い-Adjectives Vocabulary
| Word | Romaji | Meaning | Type |
|---|---|---|---|
| おおきい | Ookii | Big | い-Adj |
| ちいさい | Chiisai | Small | い-Adj |
| あつい | Atsui | Hot (Weather/Thing) | い-Adj |
| さむい | Samui | Cold (Weather) | い-Adj |
| たかい | Takai | Expensive / High | い-Adj |
| やすい | Yasui | Cheap | い-Adj |
| おいしい | Oishii | Delicious | い-Adj |
| おもしろい | Omoshiroi | Interesting / Fun | い-Adj |
| むずかしい | Muzukashii | Difficult | い-Adj |
| いい | Ii | Good | い-Adj (Irregular) |
Conversation Practice
きのう の えいが は どう でしたか。
Kinou no eiga wa dou deshitaka?
How was yesterday's movie?
とても おもしろかった です！でも、チケット は たかかった です。
Totemo omoshirokatta desu! Demo, chiketto wa takakatta desu.
It was very interesting! But, the tickets were expensive.
そう ですか。えいがかん の ポップコーン は おいしかった ですか。
Sou desuka. Eigakan no poppukōn wa oishikatta desuka?
Is that so? Was the movie theater's popcorn delicious?
いいえ、あまり おいしくなかった です。
Iie, amari oishikunakatta desu.
No, it was not very delicious.
コーヒー は どう でしたか。あつかった です か。
Kōhī wa dou deshitaka. Atsukatta desu ka.
How was the coffee? Was it hot?
はい、とても あつかった です。そして、おいしかった です！
Hai, totemo atsukatta desu. Soshite, oishikatta desu!
Yes, it was very hot. And, it was delicious!
Chapter Summary
- 1い-Adjectives always end with the character い in their dictionary form.
- 2Instead of using plain verbs to show tense, the adjective itself changes its ending.
- 3Present Negative: Drop い, add くない.
- 4Past Affirmative: Drop い, add かった.
- 5Past Negative: Drop い, add くなかった.
- 6To describe a noun directly, just put the い-adjective before it (e.g., おおきい くるま).
- 7いい (good) is irregular. All of its conjugations start with よ instead (よくない, よかった, よくなかった).
Knowledge Check
Test your ability to conjugate Japanese adjectives!
Quiz
Which of the following creates a polite PRESENT NEGATIVE ('Is not') for an い-adjective?