Homophily

Coined by sociologists Paul Lazarsfeld and Robert K. Merton in 1954 during their study of friendship formation in Addison Terrace, a biracial housing project in Pittsburgh. They defined homophily as "a tendency for friendships to form between those who are alike in some designated respect," distinguishing between status homophily (shared social characteristics) and value homophily (shared beliefs). Their work drew on Georg Simmel's theories and linked to anthropological studies of homogamy. McPherson et al.'s 2001 review documented over 100 studies observing homophily across diverse social contexts.