The reinforcement of certain beliefs by social institutions. These beliefs include
that people fall into two distinct and complementary categories, male and
female, and that sexual relations are normal only between people of different
sexes, and correlates to beliefs that each sex has certain ‘natural’ roles in life.
Thus, it is assumed that sex, gender identity and gender roles should always
align to either all-male or all-female norms, and heterosexuality is the only
‘normal’ sexual orientation.