Tau Kappa Epsilon chapters and colonies are individual organizations of initiated members of Tau Kappa Epsilon associated with a university or college. After the first, or single-letter Alpha series, chapters are named with a two-letter Greek letter combination in alphabetical order of the Greek alphabet, such as Alpha-Alpha, Beta-Alpha, etc. The Greek letter "Eta" was skipped over as a named series. Naming occurs according to the date of when the chapter's charter was granted. In one exception to this general rule, the group that would have been the Sigma chapter received special permission to be referred to as the Scorpion chapter, honoring the name of a long-standing local affiliate into the Fraternity.