fetus

American  

[fee-tuhs] / ˈfi təs /

especially British, foetus

noun

Embryology.

fetuses plural

1. (used chiefly of viviparous mammals) the young of an animal in the womb or egg, especially in the later stages of development when the body structures are in the recognizable form of its kind, in humans after the end of the second month of gestation.

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fetus British  

/ ˈfiːtəs /

noun

1. the embryo of a mammal in the later stages of development, when it shows all the main recognizable features of the mature animal, esp a human embryo from the end of the second month of pregnancy until birth Compare embryo

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fetus Scientific  

/ fē′təs /

1. The unborn offspring of a mammal at the later stages of its development, especially a human from eight weeks after fertilization to its birth. In a fetus, all major body organs are present.

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fetus Cultural  

1. The embryo of an animal that bears its young alive (rather than laying eggs). In humans, the embryo is called a fetus after all major body structures have formed; this stage is reached about sixty days after fertilization.

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Other Word Forms

Noun Inflected Forms

• fetuses
  plural

Etymology

Origin of fetus

First recorded in 1350–1400; Middle English, from Latin fētus “bringing forth of young,” hence “that which is born, offspring, young still in the womb,” equivalent to fē- (verb base attested in Latin only in noun derivatives, as fēmina “woman,” fēcundus “fertile,” fīlius “son,” fīlia “daughter,” etc.; compare Greek thēsthai “to suck, milk,” Old High German tāan “to suck,” Old Irish denid “(he) sucks,” Slavic (Polish) doić “to milk” + -tus suffix of verb action; see fecund

Explanation

A fetus is a mammal before it's born. Once upon a time, you started as an embryo, matured into a fetus, and were then thrust into the world as a newborn. Fetus is a Latin word that means "the bearing, bringing forth, or hatching of young." Even though the Latin points to a fetus "hatching," contemporary science only regards viviparous vertebrates as having fetuses. In other words, if an animal has a backbone and was delivered via live birth, it was once a fetus. If a kitten has claws, whiskers, and ears, but is still inside its mother's womb, it's a fetus. In the UK, fetus is spelled foetus.

Example Sentences

See Examples For:

fetus fetuses

It is considered the safest option for treating pain and fever in pregnant women, as other medications, including aspirin or ibuprofen, present proven risks to the fetus -- as do untreated fevers.

From Barron's ● Jul. 13, 2026

But after confirming that her fetus still had heart tones, the OB-GYN on duty, Dr. Britte Smith, said she couldn’t induce yet.

From Salon ● May 27, 2026

Included in the slideshow they posted Thursday is what appears to be a sonogram image of a fetus in a womb, throwing a “rock on” hand signal.

From Los Angeles Times ● May 14, 2026

Although prior immunity usually protects the fetus, routine screening is not available in some countries, highlighting the challenges of managing an infection that is widespread but often symptom-free.

From Science Daily ● Jan. 27, 2026

Once inside the womb, semen matured into a fetus via nourishment from the mother.

From "The Gene" by Siddhartha Mukherjee

Moms can transfer measles antibodies to their fetuses, and those can stick around for a few months after birth.

From Slate ● Feb. 17, 2026

Such tools could help detect consciousness in patients with brain injuries or dementia and determine when awareness arises in fetuses, animals, brain organoids, or even AI systems.

From Science Daily ● Feb. 1, 2026

Pregnant women typically take folate supplements to prevent neural tube defects in developing fetuses.

From The Wall Street Journal ● Sep. 24, 2025

There is some reason for optimism: The EPA last month issued a rare emergency order to stop the use of another weedkiller, dachthal, that poses a significant risk to fetuses.

From Los Angeles Times ● Aug. 31, 2024

If they slept there, she and Estha, curled together like fetuses in a shallow steel womb, what would Hulk Hogan and Bam Bam Bigelow do?

From "The God of Small Things" by Arundhati Roy