noun, plural -os, adjective | 1. | the young of a viviparous animal, esp. of a mammal, in the early stages of development within the womb, in humans up to the end of the second month. Compare fetus. |
| 2. | Botany. the rudimentary plant usually contained in the seed. |
| 3. | any multicellular animal in a developmental stage preceding birth or hatching. |
| 4. | the beginning or rudimentary stage of anything: He charged that the party policy was socialism in embryo. |
| 5. | embryonic. |

| a combining form representing embryo in compound words: embryology. |
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.”
embryo em·bry·o (ěm'brē-ō')
n. pl. em·bry·os
An organism in its early stages of development, especially before it has reached a distinctively recognizable form.
An organism at any time before full development, birth, or hatching.
The fertilized egg of a vertebrate animal following cleavage.
In humans, the prefetal product of conception from implantation through the eighth week of development.
embryo- or embry-
pref.
Embryo: embryogenesis.