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

The researchers say the findings highlight the importance of preventing infections that can be transmitted to a fetus during pregnancy.

From Science Daily ● Sep. 23, 2026

This is not the first case in which a surrogate has refused to terminate a pregnancy after the intended parents learned that the fetus had serious birth defects.

From Slate ● Sep. 17, 2026

Bush, who was arrested at Heathrow Airport after returning from a holiday in the US, was not charged with denying Ness's baby a burial because of the age of the fetus.

From BBC ● Jul. 28, 2026

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

Like they’re so mature and all-knowing, and I’m some kind of half-formed fetus.

From "What If It's Us" by Becky Albertalli and Adam Silvera

He specializes in treating high-risk pregnancies, from cases of eclampsia, hypertension, or gestational diabetes to patients with multiple fetuses.

From Slate ● Jun. 16, 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

An RSV vaccine is also available for expectant mothers at weeks 32 to 36 of pregnancy to pass protection on to their fetuses.

From Los Angeles Times ● Aug. 26, 2024

Her body curled too; as the weeks turned to months, she shrank into herself like the stiffest of fetuses, shrivelling, her skin sallow and waxy.

From "Typical American" by Gish Jen