exogamy
noun
- social arrangement where marriage is allowed only outside a social group
Wiktionary
Pronunciation: /ɛksˈɑ.ɡə.mi/
noun
Etymology: From exo- + -gamy. Coined by British lawyer and ethnologist John Ferguson McLennan in his Studies in Ancient History, page 25.
- marriage to a person belonging to a tribe or group other than one's own as required by custom or law
“The daughters of Danaüs thus apparently stand for mother-right, which usually occurs in conjunction with exogamy, marriage outside the family or clan.”
- the fusion of two unrelated gametes