Embryo Means Something That Grows Inside
An embryo is an organism in its earliest development. In humans the term applies for a defined period, then changes.
An embryo is an organism in the earliest stages of development. Human medicine uses the word for a defined window: from fertilisation until about the eighth week, after which the term becomes *foetus*. The switch marks the point at which the major organ systems have formed and growth becomes the main business.
- An organism in early development. *A frozen embryo.*
- A plant seed's germ. *The wheat embryo.*
- In embryo — in an early undeveloped form. *The plan exists in embryo.*
Word forms
| Form | Word | Example |
|---|---|---|
| Noun | embryo | A human embryo. |
| Plural | embryos | Stored embryos. |
| Adjective | embryonic | An embryonic idea. |
| Related | foetus | A developing foetus. |
| Field | embryology | The study of embryology. |
How it is used in a sentence
- The embryo becomes a foetus at about eight weeks.Human development.
- The idea is still embryonic.Undeveloped.
- Embryology studies development before birth.The field.
Stages of human development
- Zygote — the single fertilised cell
- Blastocyst — a hollow ball of cells, about five days in
- Embryo — from implantation to around eight weeks
- Foetus — from about nine weeks until birth
- Neonate — a newborn
From Medieval Latin *embryo*, from Greek *embryon*, a young one, from *en*, in, and *bryein*, to swell or grow.
Embryo or foetus?
In human medicine, embryo covers roughly the first eight weeks and foetus the period after that.
Foetus or fetus?
Foetus is the British spelling, fetus the American and the one used in most scientific journals.