An open relationship is an umbrella term for any relationship that is open to new sexual and/or romantic partners.

Specifically, it is an interpersonal relationship in which the parties want to be together but agree to a form of non-monogamous relationship. This means that they agree that other people relating in a flirting manner, sexual or physical, or intimate way with their partner is permitted, or often times tolerated. Generally, an open relationship is when the parties involved have two or more sexual relationships occurring at the same time either as a short-term relationship, such as dating, or a long-term relationship, such as marriage.