also: へき
noun
Usually refers to a personal habit, often a bad or annoying one, but can be neutral. Common in phrases like 癖になる (become a habit) or 癖がある (have a habit/peculiarity).
彼は爪を噛む癖がある。
He has a habit of biting his nails.
このゲームは癖になる。
This game is addictive (becomes a habit).
noun
peculiarity; idiosyncrasy; mannerism; quirk
Only with reading くせ / クセ
Describes a distinctive personal trait, often a small oddity or characteristic way of doing something. Overlaps with sense 1 but emphasizes uniqueness rather than repetition.
彼女の話し方には少し癖がある。
She has a slight quirk in the way she speaks.
あの作家の文体は癖が強い。
That author's writing style is strongly idiosyncratic.
noun
Only with reading くせ / クセ
Refers to a physical irregularity: a crease in paper or cloth, a kink in hair or wire, a wrinkle. Often used with つく (癖がつく) or 直す (癖を直す).
この紙には折り癖がついている。
This paper has a crease from being folded.
髪の癖が強いので、朝は大変だ。
My hair has a strong kink, so mornings are tough.