A
cotyledon is the first
leaf or one of the first pair of leaves or whorl of leaves on a newly developed
plant emerging from the
seed embryo[?]. The number of cotyledons a plant has is one common way that biologists group plant species. Plants with one cotyledon are therefore "
monocotyledons" (or simply monocots) and plants with two are "
dicotyledons" (or simply dicots).