Homogamy, a term sociologists use to mean the tendency to choose romantic partners based on similarities in background and group membership, is very common. Why?

We tend to have more access to people like ourselves.

Sociologists used the word homogamy to described the unity of the individuals who are similar to each other. This word derives from the word "homo" meaning one or similar, and "gamos" meaning marriage. This meaning makes the word suitable for the definition.