earpiece
n. countable B1 Intermediate US //ˈiɹpis// UK //ˈiəpiːs// ear·piece
n. a small piece of equipment that fits inside your ear to let you hear sound. You use it with a phone, a radio, or a headset.
n. a small, curved component of an audio device designed to fit within the ear canal. Often used in conjunction with a microphone or a second earpiece to form a headset.
He put the earpiece in his left ear to take the call.
The technician wore a single earpiece to listen to the radio while working on the engine.
Modern wireless earpieces have significantly improved in sound quality and battery life, allowing users to maintain clear communication without the physical constraints of a wired headset.