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

Hints of a Shrek surprise appeared early on, when Miss Culturista Patti Harrison revealed she was pregnant, showing her sonogram with a green, Shrek-like fetus.

From Los Angeles Times ● Jun. 18, 2026

As the human body develops from an embryo into a fetus and eventually an infant, neurons form complex communication networks between the brain and spinal cord.

From Science Daily ● May 29, 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

In the womb, the minihuman was expanded to the size of the fetus.

From "The Gene" by Siddhartha Mukherjee

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

The woman cried and begged guards for days after to help her get pills to expel the fetuses — help that did not come before Pineda left the facility.

From Los Angeles Times ● Dec. 3, 2025

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

From The Wall Street Journal ● Sep. 24, 2025

The study found that PM2.5 exposure can influence the histone profiles of pregnant women, disrupting the normal balance of cytokine genes and leading to increased inflammation in both women and fetuses.

From Science Daily ● Nov. 29, 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