noun, plural: dicotyledons
A group of flowering plants belonging to the class Magnoliopsida of Angiospermae (angiosperms), characterized by having two photosynthetic cotyledons in the seed that may emerge from the ground when the seed germinates.
The angiosperms (the flowering plants) can either be a monocotyledon (or monocot) or a dicotyledon (or dicot) according to the number of cotyledons in their seeds (which in the case of dicots the cotyledons are two, hence the name). The cotyledons of the dicots may also emerge and show above the ground and function similar to leaves (i.e. perform photosynthesis).
Apart from the number of cotyledons, other identifying characteristics are as follows: