What does foetus mean?
A foetus is the unborn offspring of a mammal during the later stages of prenatal development — in humans, the term applies from roughly the ninth week of pregnancy until birth, following the embryonic stage. At this point the major structures of the body have formed, and growth and maturation continue until delivery. The word carries significant emotional and ethical weight, featuring prominently in debates on abortion, prenatal care, and reproductive rights, so writers should be aware of its sensitivity in such contexts. 'Foetus' is chiefly a British spelling; American English uses 'fetus', and even British medical publications increasingly prefer it. The word derives from the Latin 'fetus', meaning offspring or the act of bearing young, and gives rise to adjectives such as 'foetal'. Its precise, clinical register makes it the standard term in medicine, journalism, and everyday discussion of pregnancy.
nounAn unborn offspring of a mammal, in humans developing from about the ninth week of pregnancy until birth; the standard British spelling of 'fetus'.
- An unborn mammalian offspring at the stage of development after the embryonic phase, in humans from roughly the ninth week of pregnancy until birth.
"The ultrasound revealed that the foetus was developing normally."
"Doctors monitored the foetus's heartbeat throughout the pregnancy."
"Studies showed that the foetus responds to sound from around the second trimester."
The plural follows the standard English pattern of adding '-es'. In American English the plural is 'fetuses'.
"The ultrasound confirmed that she was carrying twins — two healthy foetuses."
The 'oe' in 'foetus' was actually a Renaissance-era mistake — Latin 'fetus' has no 'o', yet the misspelling stuck in Britain for centuries.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of foetus
The word comes from the Latin 'fetus' (also spelled 'foetus' in some post-classical texts), meaning 'offspring' or 'the act of bringing forth', related to the verb 'fetuere', to bear or produce young. It entered English in the late fourteenth century via Middle English. The 'oe' spelling arose from a mistaken belief among Renaissance editors that certain Latin words contained a diphthong where none existed; classical Latin used only 'fetus'. The derivative adjective 'foetal' (American 'fetal') remains common in phrases such as 'foetal position'.
Related word forms
How foetus is actually used
This spelling predominates in British general usage, though British medical journals and international medical bodies now favour the American spelling 'fetus'. In American English, 'foetus' is rare and may be seen as an error.
Easily confused with foetus
'Fetus' and 'foetus' refer to exactly the same thing — 'foetus' is simply the traditional British spelling, while 'fetus' is the standard American spelling and the preferred form in British medical writing.