The words sex and gender are commonly used interchangeably, but many linguists would argue that their usage is quite distinct. Sex refers to the biological and physiological characteristics, while gender refers to behaviors, roles, expectations, and activities in society.
Sex refers to male or female, while gender refers to masculine or feminine.
The differences in the sexes do not vary throughout the world, but differences in gender do.
Here are some examples of characteristics related to sex:
Females have a vagina, men don't
Males have a penis, women don't
Male newborns tend to weigh more than female newborns
Females can breastfeed their babies, males can't
Males have deeper voices than females
Females can get pregnant, males can't
Males have testicles and females have ovaries
Here are some examples of characteristics related to gender:
Women tend to do more of the housework than their spouses do
A higher percentage of US doctors are women, compared to Egypt
Nursing is often seen as a woman's job, although many men enter the profession
In some countries women have to cover their heads when they go outside the house
120 years ago women were not allowed to vote in elections
Another way of putting it is:
Sex refers to a natural or biological feature.
Gender refers to cultural or learned significance of sex.