Sex refers to biology; however, there is no single, universally agreed-upon set of guidelines for defining sex. Sex is complex, dynamic, context-dependent, and interacts with gender and other social factors (Ritz & Greaves, 2022; Dubois et al., 2025).
In humans (and non-human mammals), sex traditionally refers to the biological attributes that distinguish male, female, and/or intersex according to functions that derive from the chromosomal complement (generally XX/XY), reproductive organs (internal and external genitalia), or specific hormonal, environmental, or cultural factors that affect the expression of phenotypic traits (Barresi & Gilbert, 2023; Jones, 2018; Kessler, 1998).