common-law partner
A common-law partner is someone who you’ve lived with, for at least one year, in a conjugal or marriage-like relationship. It does not matter what their sex or gender is.
Common-law also means a conjugal partner that you’ve lived with for less than a year if you could not live together because it was against the law, or because you’d be persecuted.
Common-law is defined differently in other areas of the law, like family law.