cotyledon

noun

cot·​y·​le·​don ˌkä-tə-ˈlē-dᵊn How to pronounce cotyledon (audio)
plural cotyledons
1
: the first leaf or one of the first pair or whorl of leaves developed by the embryo of a seed plant see seedling illustration
2
: a small lobe of the mammalian placenta that facilitates the delivery of oxygen and nutrients to the fetus
cotyledonary adjective
cotyledonary position

Examples of cotyledon in a Sentence

Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Vegetables: Unlike sprouts that are consumed just 3-7 days after seeds are planted, microgreens, as the name implies, are harvested for their green cotyledons (or first leaves) and stems between 1-3 weeks after their seeds are sown. Joshua Siskin, Oc Register, 17 July 2025

Word History

Etymology

New Latin, from Greek kotylēdōn cup-shaped hollow, from kotylē cup, anything hollow

First Known Use

1540, in the meaning defined at sense 2

Time Traveler
The first known use of cotyledon was in 1540

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Cite this Entry

“Cotyledon.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/cotyledon. Accessed 23 Jul. 2025.

Kids Definition

cotyledon

noun
cot·​y·​le·​don ˌkät-ᵊl-ˈēd-ᵊn How to pronounce cotyledon (audio)
: the first leaf or one of the first leaves developed by the embryo of a seed plant that is usually folded within the seed until germination and serves as a storehouse of food

called also seed leaf

Medical Definition

cotyledon

noun
cot·​y·​le·​don ˌkät-ᵊl-ˈēd-ᵊn How to pronounce cotyledon (audio)
1
: a lobule (see lobule sense 2) of a mammalian placenta that facilitates the delivery of oxygen and nutrients to the fetus
2
: the first leaf or one of the first pair or whorl of leaves developed by the embryo of a seed plant
cotyledonary adjective

More from Merriam-Webster on cotyledon

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