‘左耳’ literally means 'left ear' — a compound noun formed by combining 左 (zuǒ), meaning 'left', and 耳 (ěr), meaning 'ear'. It refers specifically to the ear on the left side of the head and is used in anatomical, medical, and everyday contexts. Unlike English, Chinese does not use articles or plural markers here; 左耳 is unmarked for number and functions as a singular count noun. It appears frequently in health-related discussions, such as describing symptoms (e.g., pain, ringing, hearing loss) localized to that side.

This term is neutral in register and commonly used across spoken and written Chinese — from doctor-patient conversations to casual descriptions ('My left ear itches') or directional instructions ('Cover your left ear'). It contrasts directly with 右耳 (yòu ěr, 'right ear'), and together they form a basic anatomical pair. While not typically used metaphorically, it may appear in idioms or expressions involving listening (e.g., in the idiom 左耳进，右耳出, 'in one ear and out the other'), though there the phrase functions idiomatically rather than referentially.