chlamydia

noun

chla·​myd·​ia klə-ˈmi-dē-ə 

plural chlamydiae klə-ˈmi-dē-ˌē 

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

klə-ˈmi-dē-əl 

adjective

Examples of chlamydia in a Sentence

Recent Examples on the Web

And cases of gonorrhea and chlamydia continued to fall, too. —Chantelle Lee, Time, 26 Sep. 2025

Planned Parenthood officials also pointed to the 2013 closure of a Shawano County clinic, which was followed by a 46% increase in cases of chlamydia in the following years, as a sign of what funding cuts can do. —Jessie Opoien, jsonline.com, 24 Sep. 2025

The World Health Organization estimates that more than 374 million new STIs occur each year worldwide, and chlamydia alone accounts for more than 1/4 of those cases among adults ages 15 to 49. —Daryl Austin, USA Today, 23 Sep. 2025

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

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

Medical Definition

chlamydia

noun

chla·​myd·​ia klə-ˈmid-ē-ə 

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  also chlamydias

a

: a bacterium of the genus Chlamydia

b

: an infection or disease caused by a bacterium of the genus Chlamydia

chlamydial

-ē-əl 

adjective