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

Many chlamydia infections are asymptomatic, but chlamydia can cause complications if left untreated. —Heidi Cope, Health, 23 Aug. 2025

This is despite decreases in cases of chlamydia and gonorrhea, according to CDC data. —Mary Kekatos, ABC News, 14 Aug. 2025

Although gonorrhea can also cause PID, very often there is a coinfection with chlamydia, ranging from 10% to 40% in some National Institutes of Health studies. —Jill Grimes, CNN Money, 13 Aug. 2025

There is a higher chance of getting an infection with chlamydia or gonorrhoea. —Tanyel Mustafa, Refinery29, 7 Aug. 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