trisomy

noun

tri·​so·​my ˈtrī-ˌsō-mē How to pronounce trisomy (audio)
plural trisomies
: the condition (as in Down syndrome) of having one or a few chromosomes triploid in an otherwise diploid set
trisomic
(ˌ)trī-ˈsō-mik How to pronounce trisomy (audio)
adjective or noun

Examples of trisomy in a Sentence

Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
But during Kiya’s second trimester, doctors discovered that their unborn son had trisomy 18. — Jordan Greene, PEOPLE, 12 Aug. 2026 March is awareness month for autoimmune disorders, bleed disorders, multiple sclerosis, colorectal cancer, endometriosis, traumatic brain injuries and trisomy, a genetic condition characterized by the presence of three copies of a specific chromosome instead of the usual pair (two copies). — Scott Lafee, San Diego Union-Tribune, 3 Mar. 2026 This trisomy leads to a multitude of changes to heart and immune function as well as neurodevelopmental impairments. — Ashley Brandebura, The Conversation, 11 Nov. 2025 Testing, however, soon revealed trisomy 18, a genetic abnormality that is usually fatal, often before birth. — Peter Slevin, New Yorker, 1 Sep. 2025 See All Example Sentences for trisomy

Word History

Etymology

tri- + -some entry 3 + -y entry 2

First Known Use

1930, in the meaning defined above

Time Traveler
The first known use of trisomy was in 1930

Browse Nearby Words

trisome
trisomy
trisomy 21
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Cite this Entry

“Trisomy.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/trisomy. Accessed 17 Aug. 2026.

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Medical Definition

trisomy

noun
tri·​so·​my ˈtrī-ˌsō-mē How to pronounce trisomy (audio)
plural trisomies
: the condition (as in Down syndrome) of having one or a few chromosomes triploid in an otherwise diploid set

More from Merriam-Webster on trisomy

Britannica.com: Encyclopedia article about trisomy

Last Updated: - Updated example sentences
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