Japanese adjectives naturally modify nouns. But what if you want an adjective to modify a verb? You need to convert it into its adverb form. The good news: the rules are dead simple. For い-adjectives, drop い and add く. For な-adjectives, drop な and add に.
い-Adjectives: Drop い, Add く
美味しい → 美味しく
| Original | Adverb Form | Example |
|---|---|---|
| 美味しい (delicious) | 美味しく | 美味しく作ります。 → Make it delicious. |
| 早い (fast/early) | 早く | 早く起きます。 → Wake up early. |
| 安い (cheap) | 安く | 安く買います。 → Buy it cheap. |
| 大きい (big) | 大きく | 大きく書いてください。 → Please write it bigger. |
The rule: drop the final い and replace it with く. This is the same beginning as the negative form (〜くない), so it's easy to remember.
な-Adjectives: Drop な, Add に
綺麗（な）→ 綺麗に
| Original | Adverb Form | Example |
|---|---|---|
| 綺麗な (pretty) | 綺麗に | 綺麗に作ります。 → Make it beautifully. |
| 静かな (quiet) | 静かに | 静かに歩きます。 → Walk quietly. |
| 上手な (skillful) | 上手に | 上手に歌います。 → Sing well. |
| 簡単な (simple) | 簡単に | 簡単に説明します。 → Explain simply. |
The rule: drop な (or just add に to the stem).
Side-by-Side Comparison
| Type | Modifying a Noun | Modifying a Verb (Adverb) | Rule |
|---|---|---|---|
| い-adjective | 美味しいケーキ | 美味しく作る | い → く |
| な-adjective | 綺麗なケーキ | 綺麗に作る | な → に |
Memory trick: い becomes く, な becomes に.
Common Combinations
The adverb form is most commonly placed before a verb to describe "how" an action is done:
- 遅く帰ります。 → Come home late.
- きれいに片付けます。 → Tidy up neatly.
- 優しく話します。 → Speak gently.
- 丁寧に書きます。 → Write carefully.
Summary
- い-adjective → drop い, add く (美味しい → 美味しく)
- な-adjective → drop な, add に (綺麗な → 綺麗に)
- Place the adverb form before a verb to describe how the action is performed
- Memory trick: い→く, な→に
Practice Quiz
Q1. Turn 「早い」 into its adverb form and make a sentence: "Please come early."
Show Answer
早く来てください。
早い → drop い, add く → 早く. Place it before the verb 「来てください」.
Q2. Turn 「静かな」 into its adverb form and make a sentence: "Please eat quietly."
Show Answer
静かに食べてください。
静かな → drop な, add に → 静かに. Place it before the verb 「食べてください」.
Q3. What do 「美味しく作ります」 and 「綺麗に作ります」 mean respectively?
Show Answer
- 美味しく作ります → Make it delicious. (い-adjective adverb: 美味しい → 美味しく)
- 綺麗に作ります → Make it beautifully. (な-adjective adverb: 綺麗な → 綺麗に)
Same verb, different adverbs — describing different qualities of the result.