cotyledon

From Latin cotylēdon, from Ancient Greek κοτυληδών (kotulēdṓn, “cup-shaped cavity”), from κοτύλη (kotúlē, “cup”).

• (UK) IPA^(key): /kɒtɪˈliːdn̩/
• (US) IPA^(key): /ˌkɑtl̩ˈiːdn̩/

cotyledon (plural cotyledons)

1. (physiology) Each of the patches of vili on the foetal chorion of ruminants and some other mammals.
   • 1997, Roy Porter, The Greatest Benefit to Mankind, Folio Society 2016, p. 72:

     Forced to apply animal findings to humans, his human womb also had cotyledons like a dog's.

2. (botany) The leaf of the embryo of a seed-bearing plant; after germination it becomes the first leaves of the seedling.

• seed leaf