A light bulb, as screwed into a lamp to light a room. Depicted as an incandescent bulb with a silver base, often shown with filament and a soft, yellow-white glow.
Commonly used to represent ideas (as over a head in a cartoon), thinking, and learning, often as paired with 🤔 Thinking Face or 💭 Thought Balloon. May also represent various senses of light and brightness.