The term sex and gender are often used interchangeably. But sex more properly refers to biological differences of male and female, while gender refers to society' s construction of a system that identifies what is masculine and feminine. Unlike the set of characteristics defining biological sex, the set of traits that are associated with gender does not sort people into two nonoverlapping groups. The traits characterize people in a complex way
that a person may have both masculine and feminine traits.
Gender traits are not determined at birth.