A cactus (pl.: cacti, cactuses, or less commonly, cactus) is a member of the plant family Cactaceae (/ k æ ˈ k t eɪ s i aɪ,-s iː iː /), a family comprising about 127 genera with some 1,750 known species of the order Caryophyllales. The word cactus derives, through Latin, from the Ancient Greek word κάκτος (káktos), a name originally used by Theophrastus for a spiny plant whose ...