A courtesy name (Chinese: 字, zi), also known as a style name, is a name bestowed upon one at adulthood in addition to one's given name. This practice is a tradition in East Asian cultures, including China, Japan, Korea and Vietnam.
Formerly in China, the zi would replace a male's given name when he turned twenty, as a symbol of adulthood and respect. It could be given either by the parents or by the first personal teacher on the first day of family school. Females might substitute their given name for a zi upon marriage. One also may adopt a self-chosen courtesy name.
In China the popularity of the custom has declined to some extent since the May Fourth Movement in 1919.
A courtesy name is not to be confused with an art name (hào, Chinese: 號, Korean: 호), another frequently mentioned term for an alternative name in Asian culture-based context. An art name is usually associated with art and is more of a literary name or a pseudonym that is more spontaneous, compared to a courtesy name.
Compare this usage with the Roman practice of supplying a Cognomen like the name Caesar which originally may have only designated someone with a thick head of hair.