mononormativity

The assumption that romantic and sexual relationships can only occur, or are only normal, between two monogamous partners

In 1969, the Trudeau Liberals partially decriminalized homosexuality by allowing homosexual acts to take place provided that only two people were present. The idea that only two people could be present stems from the concept of mononormativity, or in other words, the idea that sexual relations are acceptable when only two people take part, preferably within the confines of a monogamous relationship

The assumption that monosexuality (i.e., attraction to people of only one gender) is the only normal or significant form of sexuality.