Pronounced "HEH-ter-OH SEX-is-um"
Related terms include heteronormativity, cissexism, biphobia, queer.
"It's heterosexist to say that you don't care about gay marriage just because it doesn't directly affect your rights."
Heterosexism is the idea that heterosexuality is a normal, natural, or superior state of human sexual orientation, and the system of oppresion based on that belief. It is very closely related to homophobia and the two ideas tend to coexist. Like homophobia and cissexism, heterosexism exists on both a societal and individual level and can be either deliberate or unintentional on part of the person holding those beliefs.
Cultural heterosexism is a major obstacle in attaining marriage equality and other recognition of same-sex relationships. Related acts and ideas-- such as homophobia, biphobia, and transphobia-- can also lead to acts of violence and discrimination LGBT+ individuals.
The word heterosexism was developed as a portmanteau, from "hetero-sex," meaning "opposite sex,"and "-ism," often used as a suffix in reference to forms of oppression such as racism and sexism. Alternative terms for the same concept include institutionalized homophobia, heterocentrism, and heterosexualism.