noun, plural embryos.
the young of a viviparous animal, especially of a mammal, in the early stages of development within the womb, in humans up to the end of the second month. Compare fetus.
Botany. the rudimentary plant usually contained in the seed.
any multicellular animal in a developmental stage preceding birth or hatching.
the beginning or rudimentary stage of anything: He charged that the party policy was socialism in embryo.

1580–90; < Medieval Latin embryon-, embryo < Greek émbryon, noun use of neuter of émbryos ingrowing, equivalent to em- em-2 + bry- (stem of brýein to swell) + -os adj. suffix

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a combining form representing embryo, in compound words: embryology.
Also, especially before a vowel, embry-.
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Based on the Random House Dictionary, © Random House, Inc. 2014.
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World English Dictionary
embryo (ˈɛmbrɪˌəʊ)
n , pl -bryos
1.  an animal in the early stages of development following cleavage of the zygote and ending at birth or hatching
2.  Compare fetus the human product of conception up to approximately the end of the second month of pregnancy
3.  a plant in the early stages of development: in higher plants, the plumule, cotyledons, and radicle within the seed
4.  an undeveloped or rudimentary state (esp in the phrase in embryo)
5.  something in an early stage of development: an embryo of an idea
[C16: from Late Latin, from Greek embruon, from bruein to swell]

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Word Origin & History

mid-14c., from M.L. embryo, from Gk. embryon, in Homer, "young animal," later, "fruit of the womb," lit. "that which grows," from en- "in" + bryein "to swell, be full."
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Medical Dictionary

embryo em·bry·o (ěm'brē-ō')
n. pl. em·bry·os

  1. An organism in its early stages of development, especially before it has reached a distinctively recognizable form.

  2. An organism at any time before full development, birth, or hatching.

  3. The fertilized egg of a vertebrate animal following cleavage.

  4. In humans, the prefetal product of conception from implantation through the eighth week of development.

embryo- or embry-
Embryo: embryogenesis.

The American Heritage® Stedman's Medical Dictionary
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American Heritage
Science Dictionary
embryo   (ěm'brē-ō')  Pronunciation Key 
  1. An animal in its earliest stage of development, before all the major body structures are represented. In humans, the embryonic stage lasts through the first eight weeks of pregnancy. In humans, other placental mammals, and other viviparous animals, young born as embryos cannot thrive. In marsupials, the young are born during the embryonic stage and complete their development outside the uterus, attached to a teat within the mother's pouch.

  2. The developing young of an egg-laying animal before hatching.

  3. The sporophyte of a plant in its earliest stages of development, such as the miniature, partially developed plant contained within a seed before germination.

embryonic adjective (ěm'brē-ŏn'ĭk)
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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American Heritage
Cultural Dictionary
embryo [(em-bree-oh)]

A developing plant or animal. A plant embryo is an undeveloped plant inside a seed. An animal embryo is the animal as it develops from the single cell of the zygote until birth. Among humans and most other mammals, the embryo is carried in the mother's womb.

Note: The term is occasionally used to denote a new or developing idea or project: “The idea for the complete theory was already present in his work, in embryo form, in 1950.”
The American Heritage® New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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Example sentences
When the fertilized egg divides, it becomes an embryo.
But his cells came from macaques, not humans, and his technique involves
  destroying the embryo.
If two such eggs were combined the product would be an embryo with a poorly
  developed placenta.
Killing an embryo to obtain body parts for other human beings is totally
  unethical and barbaric in a civilized society.
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