A cactus is a member of the plant family Cactaceae, a family comprising about 127 genera with some 1750 known species of the order Caryophyllales.
The word "cactus" derives, through Latin, from the Ancient Greek κάκτος, kaktos, a name originally used by Theophrastus for a spiny plant whose identity is not certain.
Cactus have a variety of uses: many species are used as ornamental plants, others are grown for fodder or forage, and others for food (particularly their fruit).