chlamydia

noun

chla·​myd·​ia klə-ˈmi-dē-ə How to pronounce chlamydia (audio)
plural chlamydiae klə-ˈmi-dē-ˌē How to pronounce chlamydia (audio)
1
: any of a genus (Chlamydia, family Chlamydiaceae) of spherical gram-negative intracellular bacteria
especially : one (C. trachomatis) that causes or is associated with various diseases of the eye and urogenital tract including trachoma, lymphogranuloma venereum, cervicitis, and some forms of urethritis
2
: a disease or infection caused by chlamydiae
chlamydial adjective

Examples of chlamydia 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.
Baby koalas, known as joeys, can also catch chlamydia by eating pap, a substance produced by a mother that's similar to feces, if their mother is infected. Chandelis Duster, NPR, 14 Sep. 2025 Some types, especially urethritis, can arise due to gonorrhea and chlamydia, which spread through vaginal, anal, or oral sex. Mark Gurarie, Health, 13 Sep. 2025 The first vaccine to protect endangered koalas from chlamydia has officially been approved in Australia. Laura Baisas, Popular Science, 10 Sep. 2025 In the clinic’s small lab, staff can do rapid testing for HIV and syphilis and on-site testing for female patients for chlamydia, gonorrhea and trichomoniasis — which allows clinicians to prescribe medication and treat patients immediately. Nicole Blanchard, Idaho Statesman, 5 Sep. 2025 See All Example Sentences for chlamydia

Word History

Etymology

borrowed from New Latin, originally the name of a group, from Greek chlamyd-, chlamýs "mantle, chlamys" + New Latin -ia -ia entry 1

Note: The taxon Chlamydia was originally assigned to a group of microorganisms neither bacterial nor viral by Helen Jones, Geoffrey Rake, and Barbara Stearns in "Studies on lymphogranuloma venereum III. The action of the sulfonamides on the agent of lymphogranuloma venereum," Journal of Infectious Diseases, vol. 76, issue 1 (January, 1945), pp. 55-69. The choice of the element chlamyd- was presumably based on the earlier taxon Chlamydozoa (with -zoa -zoa) originated by Ludwig Halberstädter and Stanislaus von Prowazek, "Über Zelleinschlüsse parasitärer Natur beim Trachom," Arbeiten aus dem Kaiserlichen Gesundheitsamte, vol. 26, Heft 1 (1907), pp. 44-47.

First Known Use

1966, in the meaning defined at sense 1

Time Traveler
The first known use of chlamydia was in 1966

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Cite this Entry

“Chlamydia.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/chlamydia. Accessed 18 Sep. 2025.

Medical Definition

chlamydia

noun
chla·​myd·​ia klə-ˈmid-ē-ə How to pronounce chlamydia (audio)
1
capitalized : the type genus of the family Chlamydiaceae comprising coccoid to spherical gram-negative intracellular parasitic bacteria and including one (C. trachomatis) that causes or is associated with various diseases of the eye and genitourinary tract including trachoma, lymphogranuloma venereum, cervicitis, and some forms of nongonococcal urethritis
2
plural chlamydiae -ē-ˌē, -ˌī How to pronounce chlamydia (audio) also chlamydias
a
: a bacterium of the genus Chlamydia
b
: an infection or disease caused by a bacterium of the genus Chlamydia
chlamydial adjective

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