Definition of fetus in English:

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Pronunciation: /ˈfēdəs/
(British (in nontechnical use) also foetus)

noun (plural fetuses)

An unborn offspring of a mammal, in particular an unborn human baby more than eight weeks after conception.
Example sentences
  • A small subset of fetuses with large lung lesions will become hydropic, deteriorate rapidly, and die in utero.
  • Feedback is currently being used in a trial of early versus delayed delivery for preterm, growth retarded fetuses.
  • How well a woman and the fetus do during pregnancy depends upon the type of heart problem.
embryo, unborn baby/child


The spelling foetus has no etymological basis but is recorded from the 16th century and until recently was the standard British spelling in both technical and nontechnical use. In technical usage, fetus is now the standard spelling throughout the English-speaking world.


Late Middle English: from Latin, 'pregnancy, childbirth, offspring'.

  • effete from early 17th century:

    Today effete is usually used of a young man who is affected and rather effeminate, but the word originally referred to animals and meant ‘no longer fertile, too old to bear young’. It comes from Latin effetus, from ex-, meaning ‘out’, and fetus ‘breeding, childbirth, offspring’—the same word as English foetus (Late Middle English) (US fetus). The meaning developed into ‘having exhausted strength or vigour’ and in the late 18th century on to ‘feeble, over-refined’.

Words that rhyme with fetus

acetous, boletus, Cetus, Epictetus, Miletus, quietus

For editors and proofreaders

Syllabification: fe·tus

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