孝子 refers to a son who exemplifies filial piety (孝), a core Confucian virtue requiring devotion, respect, and care for one's parents. In traditional Chinese culture, the term is especially associated with the mourning period after a parent's death, when the son was expected to observe elaborate rituals (如守孝、戴孝). The concept carries deep moral weight — a 孝子 is not just any 'good son', but one who fulfills the highest social and familial obligations.