fetus

IPA/ˈfiːtəs/
KK[fˈitəs]IPA/ˈfiːtəs/

fetus — noun

  • fetussingular
  • fetusesplural

1. the standard American English spelling of 'foetus' — both forms refer to an unbo

1.noun
Definition

the standard American English spelling of 'foetus' — both forms refer to an unborn baby or young animal still developing in the womb.

Example

The ultrasound showed that the fetus was growing at a normal rate.

US spelling variant of foetus

Dr. Hugo saw that the British journal used 'foetus' where American books write 'fetus'.

Usage Note

This entry is a spelling variant. In all British English contexts, 'foetus' is the preferred spelling. In American English, 'fetus' is standard. The pronunciation is identical for both spellings.

Common Mistakes

The foetus is healthy' (in an American English document).
The fetus is healthy.
'Fetus' is the correct spelling in US English.
The doctor checked the fetus's heartbeat' (in a British English document).
The doctor checked the foetus's heartbeat.
'Foetus' is the correct spelling in UK English.

2. an unborn baby or young animal that is developing inside its mother, especially

2.nounB2
Definition

an unborn baby or young animal that is developing inside its mother, especially a human baby from roughly the end of the second month after conception until the moment of birth.

Example

Nikhil and his wife watched the fetus move its tiny arms on the ultrasound screen.

countable noun: a/the fetus

A healthy fetus depends on the mother getting enough folic acid and iron during pregnancy.

collocation: healthy fetus

Common collocations
  • developing fetus
  • healthy fetus
  • fetus grows
  • fetus develops
  • fetus moves
  • harm the fetus
  • protect the fetus
  • fetus is viable
Synonyms
  • unborn baby

    common everyday term, less technical than 'fetus'

  • unborn child

    more personal or emotional tone than 'fetus'

Usage Note

In medical contexts, 'fetus' specifically refers to the stage that begins around the eighth week of development. Before that point, the correct term is 'embryo'. Both 'fetus' (US) and 'foetus' (UK) are pronounced identically: /ˈfiːtəs/.

Common Mistakes

The embryo is eight months old.
The fetus is eight months old.
After eight weeks of development, the unborn baby is called a 'fetus', not an 'embryo'.
She is pregnant with a foetus.' (in American English).
She is pregnant with a fetus.
Use 'fetus' in US English and 'foetus' in UK English.

Word family

  • fetal
    adjectiveB2
  • fetology
    nounC2
  • fetuscide
    nounC2

Synonym discussion

Sense: noun/2

Both 'fetus' and 'embryo' refer to a developing human before birth, but they describe different stages. 'Embryo' is used for the first eight weeks after fertilization, while 'fetus' refers to the period from eight weeks until birth. 'Unborn baby' is the everyday, non-technical term that works for any stage and is preferred in casual conversation or emotional contexts. For example, a doctor would say 'The fetus is in a breech position' during a medical check-up, but the same mother might tell a friend 'My baby has been kicking all morning'. 'Unborn child' overlaps with 'unborn baby' but carries a slightly more formal or personal tone.

fetus ↗embryo ↗unborn baby

Common collocations

Nouns

Phrases

  • developing fetus
  • healthy fetus
  • fetus in the womb
  • fetus at risk

Etymology

LatinEnglish

The word enters English in the late 1300s from Latin 'fētus', meaning 'offspring' or 'bearing of young'. It is related to the Latin verb 'fētare' (to bring forth young) and to 'fēmina' (woman). The variant British spelling 'foetus' appeared in the 16th century when scholars mistakenly connected it to the Greek 'phyo' (to produce), though the Latin root has no 'o'.

First known use

14th century

14th century, in the meaning defined above