plural embryos
1
a
: an animal in the early stages of growth and differentiation that are characterized by cleavage, the laying down of fundamental tissues, and the formation of primitive organs and organ systems
especially : the developing human individual from the time of implantation to the end of the eighth week after conception
b
archaic : a vertebrate at any stage of development prior to birth or hatching
2
: the young sporophyte of a seed plant usually comprising a rudimentary plant with plumule, radicle, and cotyledons
3
a
: something as yet undeveloped
b
: a beginning or undeveloped state of something
… productions seen in embryo during their out-of-town tryout period …—Henry Hewes

embryo-

2 of 2

combining form

: embryo
embryogeny

Examples of embryo in a Sentence

Recent Examples on the Web
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Noun
His office has also suggested that people who donate sperm, eggs or embryos may need to maintain parental rights and obligations. — Romy Ellenbogen Herald, Miami Herald, 28 Oct. 2026 Using pre-implantation genetic testing, doctors can identify mutations and implant only healthy embryos. — ABC News, 27 Oct. 2026 Even alternative pathways, such as adoption, surrogacy, or gamete or embryo donation, can cost a small fortune. — The New Yorker, New Yorker, 26 Oct. 2026 Idaho doesn’t have any laws that address fertility treatments or frozen embryos, but both topics have been the subject of recent national political discussion. — Nicole Blanchard, Idaho Statesman, 22 Oct. 2026 See All Example Sentences for embryo

Word History

Etymology

Noun

Middle English embrioun "embryo, fetus," borrowed from Medieval Latin embrion-, embrio, embryo, borrowed from Greek émbryon "newborn creature (in reference to a lamb), young, embryo or fetus," from em- em- + -bryon, derivative of bry-, stem of brýein "to swell with an abundance of growth, bloom, abound," of obscure origin

Note: In Medieval Latin the Greek neuter noun émbryon was reanalyzed as the base of Latin nasal stems (such as sermōn-, sermō "speech"), resulting in the nominative singular form embryo, which was borrowed into English. The stem embryon- was employed in New Latin derivatives, the sources of embryonal and embryonic. Compare bryo-.

Combining form

Late Latin, from Greek, from embryon

First Known Use

Noun

1548, in the meaning defined at sense 1b

Time Traveler
The first known use of embryo was in 1548

Browse Nearby Words

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Cite this Entry

“Embryo.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/embryo. Accessed 29 Oct. 2026.

Kids Definition

plural embryos
1
: an animal in the early stages of development that are marked by cleavage, the laying down of the basic tissues, and the formation of primitive organs and organ systems compare fetus
2
: a tiny young plant within a seed
3
: a beginning or undeveloped stage
—used especially in the phrase in embryo

Medical Definition

plural embryos
1
archaic : a vertebrate at any stage of development prior to birth or hatching
2
: an animal in the early stages of growth and differentiation that are characterized by cleavage, the laying down of fundamental tissues, and the formation of primitive organs and organ systems
especially : the developing human individual from the time of implantation to the end of the eighth week after conception compare fetus

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