“Sex” is a biological quality or classification of sexually-reproducing organisms, generally female, male, and/or intersex, according to functions that derive from the chromosomal complement, reproductive organs, or specific hormones or environmental factors that affect the expression of phenotypic traits that are strongly associated with females or males within a given species.
Sex is a fundamental variable in all biomedical research and needs to be analysed—in human and animal research subjects, and in organs, tissues, cells, and their components. Sex may play a role in all studies involving human or non-human animals.