耳熟 (ěr shú) literally means 'ear-familiar' — combining 耳 (ěr, 'ear') and 熟 (shú, 'familiar' or 'well-known'). It describes the feeling that a sound, name, voice, or phrase is recognizable from prior hearing, even if you can’t immediately recall its source or meaning. Unlike 见过 (jiàn guò, 'seen before'), which refers to visual recognition, 耳熟 is strictly auditory — it’s about familiarity through listening.

This term is commonly used in everyday conversation when someone hears something — a person’s name, a song title, a brand, or a place name — and feels they’ve heard it somewhere before but can’t quite place it. It often appears with phrases like '听起来很耳熟' ('sounds very familiar') or '这名字有点耳熟' ('this name sounds somewhat familiar'). While not formal, it’s neutral in register and widely understood across age groups.