Cas may mean: · CaS, the chemical formula of Calcium sulfide · the standard astronomical abbreviation of Cassiopeia · Ca?, a type of cheese made in Romania. · Cas , an ancient people · Cas Guava (Psidium friedrichsthalium), a species of guava that grows in Costa Rica, and has edible fruit with an acidic taste. · Content-addressable storage · Compare_and_swap, a special atomic instruction in computer architecture. See also · CAS Cas