形容詞（けいようし）: Adjectives

Japanese Adjectives: Two Types You Must Know First

(Why Japanese adjectives feel strange — and how to stop guessing)

さむい/samui/: cold

If you’ve never learned Japanese adjectives before, start here.

In Japanese, adjectives are not all the same. Before learning how to use them, you need to know one simple fact:

Japanese adjectives come in two different types.

If you miss this step, everything that follows will feel confusing.

First things first: what is a Japanese adjective?

An adjective is a word that describes something:

• big / small

• interesting / boring

• quiet / noisy
  

In Japanese, adjectives are called けいようし (keiyoushi).

So far, so normal.

The surprise comes next.

🚦 The big idea: there are TWO kinds of adjectives

Japanese adjectives are divided into two categories:

1. i-adjectives

2. na-adjectives
   

This division is not optional. It affects how sentences are built, how meaning changes, and what sounds natural.

If you only remember one thing today, remember this.

🟦 Type 1: i-adjectives

What makes an i-adjective special?

Most i-adjectives:

• end in い

• change their own ending
  

Examples:

• たかい (expensive)

• おもしろい (interesting)

• さむい (cold)
  

These words carry grammar inside themselves.

That’s unusual if you come from English.

Why learners get confused here

In English:

interesting (affirmative) → interesting (negative)→ interesting (past)

In Japanese:

• おもしろい (is interesting)

• おもしろくない (is not interesting)

• おもしろかった (was interesting)

The adjective itself moves.

This is why Japanese adjectives often feel “verb-like”.

🟩 Type 2: na-adjectives

Now the second type.

What is a na-adjective?

na-adjectives:

• do not change themselves

• use extra grammar after them
  

Examples:

• しずか (quiet)

• きれい (beautiful)

• ひま (free / not busy)

These words behave more like nouns with descriptive meaning.

Why 「な」 exists

When a na-adjective comes before a noun, you add な:

• しずかな へや　(= a quiet room)
  

The な is not decoration. It’s a connector.

Without it, the sentence breaks.

❗ This is where most beginners get stuck

At this stage, beginners often ask:

“Is this an i-adjective or a na-adjective?”

That’s a normal question — but not the best one.

🧠 The better question (mental shortcut)

Instead, ask this:

“Does the adjective itself change?”

• If yes → i-adjective

• If no → na-adjective

This question works even when you forget labels.

🔹 How i-adjectives change (simple pattern)

Example: たかい (high/expensive)

Meaning	Form
is expensive (present affirmative)	たかい
is not expensive (present negative)	たかくない
was expensive (past affirmative)	たかかった
was not expensive (past negative)	たかくなかった

Polite speech just adds です:

• たかいです = is expensive

• たかくなかったです = was not expensive
  

⚠️ いい (good) is slightly irregular!! The first い has to change into よ in all the forms except the present affirmative: いい　

→　いい (present affirmative) →　よくない (present negative) →　よかった (past affirmative) →　よくなかった (past negative)

🔸 How na-adjectives work instead

Example: しずか (quiet)

The adjective itself never changes.

Meaning	Form
is quiet (present affirmative)	しずかだ
is not quiet (present negative)	しずかじゃない
was quiet (past affirmative)	しずかだった
was not quiet (past negative)	しずかじゃなかった

The grammar comes after the word.

That’s the key difference.

⚠️ Common beginner mistakes (you are not alone)

❌ しずかくない ❌ きれいかった ❌ たかいじゃないでした

These feel logical in English — but Japanese doesn’t stack meaning that way.

Once you understand the two types, these mistakes stop happening.

🎉 Why this matters (the fun part)

When adjectives finally make sense, you can:

• give opinions naturally

• complain politely

• sound adult instead of robotic

• adjust tone (casual vs polite)
  

Example:

• その えいがは おもしろくなかったです。 = That movie was not interesting/funny.
  

This sounds neutral, natural, and very Japanese.

Basic Adjectives: 1. I-adjectives

Japanese	Meaning (English)	Type
おおきい	big	i-adjective
ちいさい	small	i-adjective
あたらしい	new	i-adjective
ふるい	old	i-adjective
いい	good	i-adjective
わるい	bad	i-adjective
たかい	expensive / high	i-adjective
やすい	cheap	i-adjective
はやい	fast / early	i-adjective
おそい	slow / late	i-adjective
おもしろい	interesting	i-adjective
つまらない	boring	i-adjective
むずかしい	difficult	i-adjective
やさしい	easy / kind	i-adjective
さむい	cold (weather)	i-adjective
あつい	hot (weather / objects)	i-adjective
つめたい	cold (to touch)	i-adjective
いそがしい	busy	i-adjective
たのしい	fun	i-adjective
かなしい	sad	i-adjective

2. Na-adjectives

Japanese	Meaning (English)	Type
しずか	quiet	na-adjective
にぎやか	lively	na-adjective
きれい	beautiful / clean	na-adjective
ひま	free / not busy	na-adjective
べんり	convenient	na-adjective
だいじょうぶ	okay / fine	na-adjective
たいへん	tough / hard	na-adjective
すき	like	na-adjective
きらい	dislike	na-adjective
じょうず	good at	na-adjective
へた	bad at	na-adjective
げんき	healthy / energetic	na-adjective
まじめ	serious	na-adjective
かんたん	simple / easy	na-adjective
たいせつ	important	na-adjective