Cacti are succulent perennial plants. Cacti generally have thick herbaceous or woody chlorophyll-containing stems. Cacti can be distinguished from other succulent plants by the presence of areoles, small cushionlike structures with trichomes (plant hairs) and, in almost all species, spines or barbed bristles (glochids). Areoles are modified branches, from which flowers, more branches, and leaves (when present) may grow.
The cactus belongs to the family Cactaceae, which encompasses almost 2,000 different species, according to the Aggie Horticulture website of Texas A&M University. The cactus is an iconic representation of desert plant life, known for its prickly needles and often towering height. The plural form of cactus is “cacti,” and there are a number of descriptions of certain traits that identify a plant as a cactus.