く (adjective continuative)

• Reading: く
• Romaji: ku
• Formation: い-Adjective stem + く + Clause / Verb

Meaning

The continuative form of い-adjectives, created by replacing the final い with く. It is used to connect adjective clauses, form adverbs, and link to other predicates.

The く form of い-adjectives (also called the 連用形) serves multiple grammatical functions. It connects adjective clauses in a formal/written style (美しく、静かな場所 'a beautiful, quiet place'), creates adverbs (早く走る 'run fast'), and connects to auxiliary verbs like なる and する (大きくなる 'become big', 安くする 'make cheap'). In written Japanese, the く form can connect clauses sequentially, similar to the Vます continuative for verbs. It also appears in the negative form: ～くない (not ～) and ～くて (～ and/and so). The く continuative in clause-linking is more formal than くて.

Examples

1. 部屋を明るくして勉強した。 I made the room brighter and studied.
2. 冬になると日が短くなる。 When winter comes, the days become shorter.
3. 彼女は静かに、そして優しく話した。 She spoke quietly and gently.

Usage Guide

Context: spoken, written, everyday

Tone: descriptive

Do Say

• 音を小さくしてください。
• 彼は足が速く、チームで一番だ。
• 天気が良く、散歩には最適だった。

Don't Say

• 静かく話してください。(静か is a な-adjective, not an い-adjective; it cannot take く) → 静かに話してください。
• 危ないく走るな。(The correct adverb form is 危なく, not 危ないく) → 危なく走るな。

Origin & History

The く form is the 連用形 of い-adjectives, dating back to classical Japanese where it functioned identically. It is one of the most fundamental conjugation forms in the language.

Cultural Context

Generation: All ages

Social background: Universal