a social club for male undergraduates
"The new fraternity held its annual mixer on the main quad to welcome incoming freshmen."
The quality of being brothers or brotherly; brotherhood.
In plain English: A fraternity is an organization of men who share common interests and support each other, often found at colleges.
"The students wore their fraternity colors during homecoming week."
Usage: Use this term to describe close male camaraderie, but avoid confusing it with the specific social organization known as a college fraternity unless that distinction is necessary. In formal contexts regarding group dynamics, prefer "brotherhood" over "fraternity," which often carries connotations of hazing or exclusive membership in American English.
The word "fraternity" entered English in the late 14th century via Old French and Latin. It originally referred to a brotherhood or state of being brothers before evolving into its modern sense of an organization for men with shared interests.