A lover is a person you connect with in love and have a sexual relationship with. Generally the term is used more loosely by people that are polyamorous, but the term originated around this relationship being one that wasn't a primary relationship. 'Lovers' used to not always be known to the public and was a word often used to describe a partner out-side of marriage (or an affair) / cheating in a monogamous relationship.

Nowadays the relationship often implies that the relationship is either happening at the same time as other relationships in the form of Ethical non monogamy or isn't following traditional relationship patterns (e.g: intending on marriage).