Heterosexual / Straight & Heteroflexible / Homoflexible

Emotional, romantic, and/or sexual attraction primarily to people of a different gender.

Greek heteros (other) + Latin sexus (sex). Coined by Karl-Maria Kertbeny in 1868 in a private letter; first appeared in print in an anonymous German pamphlet in 1869.

A historical irony: "heterosexual" was coined by a gay rights activist. Karl-Maria Kertbeny (1824-1882) was lobbying against Prussian sodomy laws and needed a contrast term. "Heterosexuality" as a named identity category is a late 19th-century invention; the concept of a "heterosexual person" as a distinct human type did not exist before this period. Historian Jonathan Ned Katz's The Invention of Heterosexuality (1995) argued the entire hetero/homo binary is a modern cultural invention.

• "Heterosexuality is the 'natural' or 'default' orientation." All sexual orientations are natural variations of human sexuality.