What do you call a partnership between two unrelated adults who choose to share their lives together with mutual responsibilities?

A domestic partnership is a legal or personal relationship between two individuals who choose to live together and share their lives, typically with an agreement on mutual responsibilities and support, akin to marriage but not necessarily involving the formal legal status of marriage. This terminology often applies to couples who may not wish to engage in traditional marriage, opting instead for a recognized partnership that provides similar rights and obligations, particularly in areas such as healthcare, inheritance, and other legal benefits.

The other concepts mentioned while related, differ in context and formal recognition. Marriage typically involves a legal contract that affords numerous rights and responsibilities recognized by society and government, while cohabitation describes living together without formal legal recognition, and common-law relationships may provide some similar legal recognition after meeting certain criteria over time but often require the couple to live together for a specific duration.