起…作用【qǐ … zuòyòng】

起…作用 means "to play a role, to have an effect". 作用 is the noun "effect, role", and 起 is the verb. An adjective between them says how big or what kind. The frame is neutral to written.

对 + noun before 起 says what the effect is on. 起到 stresses that the effect was achieved, and goes with 的作用: 起到了…的作用.

"It doesn't work"

On its own, 起作用 means "to work, to take effect", and its negative is the everyday way to say a remedy or a method did nothing.

Not 玩 or 扮演

English "play a role" doesn't carry over word for word. 玩 is "play" as in games. 扮演…角色 is "play a part" as an actor plays one, and is used of people's roles, not of effects.

• × 他玩了一个重要的作用 → 他起了重要的作用
• × 这个药扮演了作用 → 这个药起了作用