agavaceae: chiefly tropical and xerophytic plants: includes Dracenaceae (Dracaenaceae); comprises plants that in some classifications are divided between the Amaryllidaceae and the Liliaceae
monocot family: family of flowering plants having a single cotyledon (embryonic leaf) in the seed
all-or-none law: (neurophysiology) a nerve impulse resulting from a weak stimulus is just as strong as a nerve impulse resulting from a strong stimulus