叔叔

叔叔 (shūshu) literally means 'father's younger brother.' Unlike English 'uncle,' which lumps together every parental sibling, Chinese kinship is specific: 叔叔 is only your father's younger brother — your father's older brother is 伯伯 (bóbo), and a mother's brother is 舅舅 (jiùjiu). The much more common everyday use is as a polite form of address: a child or young person calls any unrelated adult man about their parents' age 叔叔, the way an English-speaking child might say 'mister.'

You'll hear kids say 叔叔好 to a neighbor, a delivery driver, or a family friend. The reduplicated 叔叔 is the spoken form; the single character 叔 is mostly written, used in compound titles.