SUI usually means Switzerland. In sports, it’s the code used for Switzerland because it comes from the French name Suisse.

For clarity:

  • SUI = Switzerland in Olympic/FIFA-style country codes.
  • Switzerland’s official Latin name is Confoederatio Helvetica , which is why you also see CH in web domains.

If you meant a different context, such as the Sui language or the Sui dynasty, that refers to something else entirely.