homophily

Homophily is the tendency of individuals to associate with others who are similar to themselves in particular attributes, such as age, race, education, religion, or interests. In social networks and society, homophily contributes to the formation of clusters where members share characteristics, and to patterns of ties that are more likely between like individuals than between unlike ones.

There are two main mechanisms: selection, where people choose friends or partners similar to themselves, and socialization, where individuals become more similar through interaction. Researchers measure homophily with metrics such as assortativity, which captures the correlation between connected nodes with respect to attributes, and mixing matrices that summarize the distribution of ties across attribute categories.

Homophily appears across many contexts. In friendships and teams, people tend to cluster by race, age, education, and interests; in romantic and marital markets, assortative mating by education and socioeconomic status is common; and in online networks, interest- and identity-based groups form around shared topics.

While homophily can facilitate coordinated behavior and efficient information exchange within groups, it can also reinforce segregation and limit exposure to diverse perspectives. The concept is central to debates about social equity, echo chambers, and the design of interventions that reach multiple communities.