noun. A leaf of the embryo of a seed plant, which upon germination either remains in the seed or emerges, enlarges, and becomes green.

noun. One of the lobules constituting the uterine side of the mammalian placenta, consisting mainly of a rounded mass of villi.

noun. The leaf of the embryo of a seed-bearing plant; after germination it becomes the first leaves of the seedling.

""Eugene," Edith said, in the manner of a classic advertising campaign, "as long as you're up -- will you look up the definition of the word cotyledon?""

seed leaf