Felis domestica, a small animal that usually lives in house provided by its staff.
Felis Felis sylvestris catus, from an alternate (and detailed) phylogeny (at least you can see why cat). See http://www.fmnh.helsinki.fi/users/haaramo/Metazoa/Deuterostoma/Chordata/Synapsida/Eutheria/Carnivora/Aeluroidea/Felinae.htm for more...
cat, a small utility that usually lives in bin provided by root's staff. PBO