At a glance
An い-adjective changes its final い to く to describe how an action is done, like "-ly" in English. The く form goes before the verb.
[い-adjective without い] + く + Verb
はやい → はやく + はしります
田中さんは速く走ります。 Mr. Tanaka runs fast.
How to form it
Drop the final い and add く. The adjective いい is irregular and becomes よく.
| Adjective | Adverb form | Example | Meaning |
|---|---|---|---|
| 早い early | 早く | 早く起きる | get up early |
| 大きい big | 大きく | 大きく書く | write big |
| 楽しい fun | 楽しく | 楽しく遊ぶ | play happily |
| いい good (exception) | よく | よく寝る | sleep well |
| きれい (な-adjective) | きれいに | きれいに書く | write neatly |
The く form does not change. Only the verb conjugates: 早く起きます, 早く起きません, 早く起きました.