'Sigma-Chi' is the name of a fraternity in the North American college system.
Fraternities are all-male organisations found on university campuses in the U.S.A.,which provide social activities, and may have their own premises known as 'chapter houses'. Membership generally involves some sort of ritual 'initiation ceremony'.
The female equivalents of such societies are known as sororities.
Fraternities and Sororities are generally given names which include either two or three letters of the Greek alphabet. They are, therefore, sometimes known as Greek letter organisations or Greek societies.
These organisations may also exist within the high school system. A short story by Sylvia Plath entitled 'Initiation' (published in Johnny Panic and the Bible of Dreams) is based on her own high school experience of joining a sorority.