Ménage à trois 三角家庭
A ménage à trois (French for "household of three") is a domestic arrangement in which three people having romantic and/or sexual relations with each other occupy the same household. It is a form of polyamory. Ménage à quatre meanwhile refers to having four people having romantic/sexual relations with each other under one household (Not to be confused with foursome, which includes four people having sex or engaging in sexual activities at the same time).