N5 · Adjectives and adverbs
i-adjectives
the i-adjective
An adjective that ends in い, goes straight before a noun and can end a sentence on its own.
An i-adjective is a word such as 高い (expensive, tall), 新しい (new) or 寒い (cold). It ends in い, and that い is an ending rather than part of the root: every other form is built by changing it. Before a noun the adjective stands as it is, with nothing in between — 高い山, "a high mountain" — just as an English adjective does.
At the end of a sentence the bare adjective is already a complete sentence in plain style: 寒い。 means "It is cold." No verb "to be" is needed, because the adjective itself is the predicate. In polite style you add です: 今日は寒いです。 Here です does not mean "is"; it only raises the level of politeness, which is why it never changes for tense after an i-adjective. The past goes on the adjective itself.
English speakers make two mistakes with this. The first is adding だ in plain style — 寒いだ — because だ feels like "is". But だ belongs after nouns and na-adjectives, and an i-adjective does not need it. The second is putting な or の between the adjective and its noun: 高いな山 and 高いの山 are both wrong.
Not every word that ends in い is an i-adjective. きれい (pretty, clean) and 嫌い (disliked) end in い by accident and are na-adjectives: きれいな部屋. The test is whether the い disappears in other forms — 高くない drops it, きれいじゃない keeps it.
The form
stem (regular) ending auxiliary verb
| it is expensive (plain) | 高い |
| it is expensive (polite) | 高いです |
| an expensive watch | 高い時計 |
| new | 新しい |
| cold | 寒い |
| not an i-adjective: a pretty flower | きれいな花 |
The rules one by one
An i-adjective goes straight before its noun, with nothing in between.
新しい車を買いました。I bought a new car.
At the end of a plain sentence the adjective stands alone; never add だ.
この本は面白い。This book is interesting.
In polite style add です, which adds politeness and nothing else.
東京の夏は暑いです。Summer in Tokyo is hot.
The final い is the ending, and every other form is built on what comes before it.
高い、高くない、高かったexpensive, not expensive, was expensive
A closer look
Why です after an i-adjective is a special case
Strictly, です is the polite form of だ, and だ cannot follow an i-adjective. So why can です? Because the language needed a simple polite form for adjectives, and です was taken over to do that one job. An older polite form survives in set phrases: ありがとうございます and おめでとうございます are polite forms of the adjectives ありがたい and めでたい.
The practical consequence is that です after an i-adjective never carries tense. "It was cold" is 寒かったです, with the past on the adjective, and never 寒いでした.
Exceptions and special cases (1)
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the adjective is いい, "good"
the present looks regular, but every other form is built on よ: よくない, よかった.
この映画はとてもよかったです。This film was very good.
いい is a worn-down spoken form of the older よい. It replaced よい only in the present; the other forms were never rebuilt on it.
How to spot it
- 〜い
- 〜いです
- とても〜い
- あまり〜くない
Example sentences
この部屋は明るいです。This room is bright.
駅の近くに新しいカフェがあります。There is a new café near the station.
今日はとても暑いですね。It's very hot today, isn't it?
兄は背が高いです。My older brother is tall.
安い店を探しています。I am looking for a cheap shop.
このラーメン、おいしい！This ramen is delicious!
8 more example sentences
日本語の勉強は楽しいです。Studying Japanese is fun.
冷たい水をください。Cold water, please.
あの白い建物は病院です。That white building is a hospital.
古い町が好きです。I like old towns.
このかばんは重いです。This bag is heavy.
祖母の家は広いです。My grandmother's house is spacious.
早い電車に乗りましょう。Let's take an early train.
青い空がきれいです。The blue sky is beautiful.
Worth knowing (2)
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Only some colours are i-adjectives
A handful of colour words are i-adjectives: 赤い, 青い, 白い, 黒い, and with a slightly different shape 黄色い and 茶色い. Most others, such as 緑, are nouns and join their noun with の: 緑の葉.
赤い傘と緑のかばんがあります。There is a red umbrella and a green bag.
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おおきな and ちいさな
Next to 大きい and 小さい there are the forms 大きな and 小さな, which can only stand before a noun. They mean the same and often sound a little softer or more storylike. They never end a sentence: 大きなです does not exist.
公園に大きな木があります。There is a big tree in the park.
The trap English speakers fall into
Watch out
An i-adjective is already the predicate, so plain style needs nothing after it. だ is what a noun or a na-adjective needs; after an i-adjective it is simply wrong. In polite style 寒いです is fine, because です there marks politeness, not "is".
An i-adjective needs no verb: it stands before a noun as it is, and ends a sentence on its own.
Your turn
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