‘叔叔’ (shū shu) is a compound noun formed by reduplicating the character 叔, which on its own means ‘younger paternal uncle’ — that is, the younger brother of one’s father. When doubled, it becomes a general, respectful term for any paternal uncle (regardless of age relative to the father) and, more broadly, an honorific used for unfamiliar or familiar older men who are roughly the same age as one’s parents. It conveys warmth and politeness, especially in face-to-face interactions with male elders or family friends.

The term is commonly used by children and young adults when addressing or referring to such men. Unlike formal titles like 先生 (xiān sheng), ‘叔叔’ carries familial overtones and implies approachability and familiarity. It is not used for maternal uncles — those are called ‘舅舅’ (jiù jiu). In urban settings, children may even address friendly neighborhood shopkeepers or teachers’ husbands as ‘叔叔’ as a sign of respect and affection.