Sex: A medical term designating a certain combination of gonads, chromosomes, external gender organs, secondary sex characteristics and hormonal balances. Common terms are “male, “female” and “intersex.”
Gender: A socially constructed system of classification that ascribes qualities of masculinity and femininity to people. Gender characteristics can change over time and are different between cultures.
Gender Equity Resource Center
Although the two terms sex and gender are often used interchangeably, they are not the same. What follows is a brief overview of sex and gender and how they differ.
Sex = biology (female/male)
Biologically, woman is defined as an adult human female and man is defined as an adult human male.
Female = XX sex chromosomes that determine female genitalia (vagina, ovaries), female secondary characteristics (breasts, etc.), etc.
In summary, women = XX
Male = XY sex chromosomes that determine male genitalia (penis, testes), male secondary characteristics (beards, etc.), etc.
In summary, men = XY
While sex chromosomal variations exist, all people have only X or Y sex chromosomes. Variations of XX/XY are rare and considered disorders of sex development.
Sex is constant across cultures and time. A girl born in one country is biologically similar to a girl born in another since, excluding disorders or health issues, both will experience female biological realities (having a period, ability to become pregnant and/or breastfeed, menopause, etc). Regardless of what sex is called or considered individually or culturally, these realities exist for girls and women all over the world.
In summary, sex: related to biology, may be called a biological construct/classification (it is determined by natural divisions among humans, e.g. sexual dimorphism, the difference in appearance between females and males of a species)
Think, what does it mean to be a female or a male in the world? Would my experiences with my body change in other places or are these experiences the same?
Gender = culture (femininity/masculinity)
Gender is assigned based upon perceived sex. It includes all the roles, activities, values and behaviors attributed to and deemed appropriate for each sex.
Women are prescribed femininity, i.e. the roles, activities, values and behaviors attributed to and deemed appropriate for women
Men are prescribed masculinity, i.e. the roles, activities, values and behaviors attributed to and deemed appropriate for men
Gender varies across cultures and time. A girl born in one country may have significantly different experiences with gender than a girl born in another since gender is a socially constructed set of roles and characteristics attributed to and deemed appropriate for women and men by society. Gender may be referred to as gender roles, sex roles or gender stereotypes.
In summary, gender: related to culture, may be called a social construct/classification (it is determined by artificial divisions among humans, e.g. perceived differences attributed to biology)
Think, what does it mean to be feminine or masculine in the world? Would my experiences with expected behavior and personality change in other places or are these expectations the same?
In summary, sex recognizes a difference while gender creates one.
Britta N. Torgrimson, Christopher T. Minson. Sex and gender: what is the difference? Journal of Applied Physiology Published 1 September 2005 Vol. 99 no. 3, 785-787 at http://jap.physiology.org/content/99/3/785