Merriam-Webster Collegiate Dictionary - fraternity

 noun  (plural -ties)  Date: 14th century  1. a group of people associated or formally organized for a common purpose, interest, or pleasure: as  a. a fraternal order  b. guild 1  c. a men's student organization formed chiefly for social purposes having secret rites and a name consisting of Greek letters  d. a student organization for scholastic, professional, or extracurricular activities a debating ~  2. the quality or state of being brothers ; brotherliness  3. persons of the same class, profession, character, or tastes the racetrack ~