8½ Souvenirs was an American swing jazz band active from approximately 1993 to 2000 and based in Austin, Texas. The band was signed to the RCA Victor label and had two releases under that label, as well as two other releases under Austin, Texas indie labels. The band was named in tribute to the Federico Fellini film 8½ and the Django Reinhardt song "Souvenirs. " The band was instrumental in that city's 1990s Swing Revival dance scene centered at the Continental Club.
In logic and philosophy, S5 is one of five systems of modal logic proposed by Clarence Irving Lewis and Cooper Harold Langford in their 1932 book Symbolic Logic. It is a normal modal logic, and one of the oldest systems of modal logic of any kind.