foetus

IPA/ˈfiːtəs/
IPA/ˈfiːtəs/

foetus — noun

  • foetussingular
  • foetusesplural

1. a human or animal that is still growing inside its mother's body, once it has be

1.nounC1
Definition

a human or animal that is still growing inside its mother's body, once it has begun to form organs like a heart, brain, and limbs — usually from about the eighth week of pregnancy in humans.

Example

Mizuki saw her foetus on the ultrasound screen during her twelve-week scan.

common context: ultrasound scan + week count

By twenty weeks, the foetus can usually hear sounds from outside the mother's body.

typical pattern: by [N] weeks, the foetus + ability verb

Common collocations
  • developing foetus
  • viable foetus
  • harm the foetus
  • the foetus's heartbeat
  • the foetus's growth
Synonyms
  • fetus

    American English spelling of the same word

  • unborn baby

    everyday phrase; warmer and less clinical, used by parents and in news writing

  • embryo

    earlier stage of development; in humans, before about eight weeks, when organs are only just beginning to form

Antonyms
  • newborn

    a baby that has just been born, no longer inside the mother

Grammar Patterns

a/the foetus

foetus + of [number] weeks

Usage Note

British spelling; American English uses 'fetus'. Mostly used in medical, scientific, or formal writing — in everyday speech a pregnant person is more likely to say 'the baby'.

Common Mistakes

Élise is pregnant with a foetus.
Élise is pregnant.
speakers don't normally say someone is pregnant 'with a foetus'; the word belongs to medical or technical contexts.
The fetus kicked for the first time.' (in a UK textbook)
The foetus kicked for the first time.
keep spelling consistent with the variety of English used in the document.

Word family

Synonym discussion

Sense: noun/1

In humans, 'embryo' refers to the very earliest stage of development — roughly the first eight weeks after fertilisation, when the basic body plan is still forming. Once recognisable organs such as the heart and limbs have started to appear, the same developing being is called a 'foetus' (or 'fetus' in American English). 'Foetus' is the standard term in medicine, biology, and formal writing; doctors will say 'the foetus is measuring normally for twenty weeks'. 'Unborn baby' covers the same idea but is warmer and more emotional, common in parenting magazines and news stories: 'doctors saved the unborn baby's life'. Pregnant people themselves usually just say 'the baby'.

foetus ↗embryo ↗unborn baby

Common collocations

Nouns

  • foetus heartbeat
  • foetus development
  • foetus position

Phrases

  • developing foetus
  • viable foetus
  • the health of the foetus

Prepositions

  • of [a species]

Etymology

LatinEnglish

Borrowed into English in the late 1300s from Latin 'fetus', meaning 'offspring' or 'bringing forth', related to the verb 'fetare' (to breed). The spelling 'foetus' arose in later British scientific writing under the mistaken belief that the Latin had an 'oe' diphthong; modern American English has reverted to the original 'fetus', while British medical English keeps 'foetus' alongside it.