1
: arising spontaneously or from an obscure or unknown cause : primary
idiopathic epilepsy
2
: peculiar to the individual

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Idiopathic joins the combining form idio- (from Greek idios, meaning "one's own" or "private") with -pathic, a form that suggests the effects of disease. The combining form idio- is typically found in technical terms. Examples include idiographic, meaning "relating to or dealing with something concrete, individual, or unique"; idiolect, meaning "the language or speech pattern of one individual at a particular period of life"; and idiotype, meaning "the molecular structure and conformation of an antibody that confers its antigenic specificity." A more common idio- word is idiosyncrasy, which most commonly refers to an unusual way in which a person behaves or thinks, or to an unusual part or feature of something.

Examples of idiopathic in a Sentence

Recent Examples on the Web
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In court, Nugent's lawyer Chirag Patel told Magistrate Allison Vaughan that his suffered from idiopathic transverse myelitis, a neurological condition, as well as a concussion. — CBS News, 21 Oct. 2026 Patel said Nugent suffered from a neurological condition, idiopathic transverse myelitis, and a concussion. — Rod McGuirk, Los Angeles Times, 21 Oct. 2026 Syndax Pharmaceuticals — Shares tumbled 16% after the company said axatilimab did not meet its primary endpoint during a Phase 2 trial in which the antibody was used to treat idiopathic pulmonary fibrosis. — Darla Mercado, Cfp®,fred Imbert, CNBC, 13 Oct. 2026 As sure as the sun rises, Crohn’s disease is most definitely not juvenile idiopathic arthritis. — John Mildenberger, STAT, 2 Oct. 2026 See All Example Sentences for idiopathic

Word History

First Known Use

1669, in the meaning defined at sense 1

Time Traveler
The first known use of idiopathic was in 1669

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Cite this Entry

“Idiopathic.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/idiopathic. Accessed 25 Oct. 2026.

Medical Definition

idiopathic

adjective
: arising spontaneously or from an obscure or unknown cause : primary
idiopathic epilepsy
idiopathic thrombocytopenic purpura
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