noun
in-law; relative by marriage; affinity relation
Formal or legal term for a relative through marriage, as opposed to a blood relative (血族). Often used in legal contexts such as family registration.
See also: 血族
民法では、姻族は配偶者の血族を指す。
Under the Civil Code, an in-law refers to a blood relative of one's spouse.
姻族関係は離婚によって終了する。
The affinity relationship ends upon divorce.