an·​ti·​gen | \ ˈan-ti-jən How to pronounce antigen (audio) , -ˌjen \

Definition of antigen

: any substance (such as an immunogen or a hapten) foreign to the body that evokes an immune response either alone or after forming a complex with a larger molecule (such as a protein) and that is capable of binding with a product (such as an antibody or T cell) of the immune response

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Other Words from antigen

antigenic \ ˌan-​ti-​ˈje-​nik How to pronounce antigen (audio) \ adjective
antigenically \ ˌan-​ti-​ˈje-​ni-​k(ə-​)lē How to pronounce antigen (audio) \ adverb
antigenicity \ ˌan-​ti-​jə-​ˈni-​sə-​tē How to pronounce antigen (audio) \ noun

Did You Know?

An antibody is a protein produced by your immune system to fight outside invaders. Since the enemy substance actually triggers the production of antibodies, such substances are called antigens—anti- being short for antibody, and -gen meaning "producer". (In a similar way, an allergen produces an allergy, and a pathogen produces a pathology or disease.) Antigens are often rodlike structures that stick out from the surface of an invading organism—usually a bacterium or a virus—and allow it to attach itself to cells in the invaded body. But unfortunately for them, in doing so they let the immune system know they're present, and the body is flooded with an army of Pac-Man-like antibodies.

Examples of antigen in a Sentence

Recent Examples on the Web Mayo Clinic officials say a doctor may recommend a PCR (polymerase chain reaction) test to confirm a negative antigen test result. Brieanna J. Frank, The Arizona Republic, "Arizona's COVID-19 death count nears 17,100 as state reports 819 new cases, 30 deaths," 10 Apr. 2021 Before any passports get stamped, travelers receive a rapid antigen test and wait 30 minutes for a result. Gregory Barber, Wired, "Variant Hunters Race to Find New Strains Where Testing Lags," 9 Apr. 2021 An antigen test followed by a PCR test confirmed his Covid-19 diagnosis this weekend, according to Fernández's medical team. Claudia Rebaza, CNN, "Argentina's President tests positive for Covid-19 after vaccine," 4 Apr. 2021 The Giants encourage fans to take a PCR-type test, not a rapid antigen test. Ron Kroichick, San Francisco Chronicle, "Giants fans will need negative coronavirus test or vaccination proof to attend games," 1 Apr. 2021 Attendees received their antigen test results in 10 to 15 minutes via an app on their phones. NBC News, "5,000 fans pack Barcelona rock concert after Covid-19 tests," 28 Mar. 2021 Results will be valid for 72 hours for a PCR test and six hours for an antigen test. Elizabeth Weise, USA TODAY, "New York launches nation's first 'vaccine passports.' Others are working on similar ideas, but many details must be worked out.," 26 Mar. 2021 The resort fully reopened this month with a host of safety protocols in place, including the need for a rapid antigen test in a private lounge upon arrival. Sandra Ramani, Robb Report, "This Caribbean Resort Is Offering Covid-Positive Guests a Suite or a Private Jet Home—at No Charge," 23 Mar. 2021 Unvaccinated travelers are also allowed to visit Ecuador and its famous island archipelago with proof of a negative antigen test taken within 72 hours of departure, or proof of recent recovery from COVID-19. Meena Thiruvengadam, Travel + Leisure, "Vaccinated Travelers Can Now Visit Ecuador, Including the Galapagos Islands," 19 Mar. 2021

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'antigen.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of antigen

1908, in the meaning defined above

History and Etymology for antigen

German, from French antigène, from anticorps antibody + -gène -gen

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Time Traveler for antigen

Time Traveler

The first known use of antigen was in 1908

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Statistics for antigen

Last Updated

13 Apr 2021

Cite this Entry

“Antigen.” Dictionary, Merriam-Webster, Accessed 14 Apr. 2021.

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More Definitions for antigen



English Language Learners Definition of antigen

medical : a harmful substance that causes the body to produce antibodies


an·​ti·​gen | \ ˈant-i-jən How to pronounce antigen (audio) \

Medical Definition of antigen

: any substance (as an immunogen or a hapten) foreign to the body that evokes an immune response either alone or after forming a complex with a larger molecule (as a protein) and that is capable of binding with a product (as an antibody or T cell) of the immune response

Other Words from antigen

antigenic \ ˌant-​i-​ˈjen-​ik How to pronounce antigen (audio) \ adjective
antigenically \ -​i-​k(ə-​)lē How to pronounce antigen (audio) \ adverb

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More from Merriam-Webster on antigen

Nglish: Translation of antigen for Spanish Speakers

Britannica English: Translation of antigen for Arabic Speakers Encyclopedia article about antigen

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