cotyledon

cot·y·le·don

noun \ˌkät-^əl-ˈēd-^ən\

Definition of COTYLEDON

1

: a lobule of a mammalian placenta

2

: the first leaf or one of the first pair or whorl of leaves developed by the embryo of a seed plant or of some lower plants (as ferns)

—cot·y·le·don·ary \-ˈēd-^ən-ˌer-ē\ adjective