pen·​i·​cil·​lin | \ˌpe-nə-ˈsi-lən \

Definition of penicillin 

1 : any of several relatively nontoxic antibiotic acids of the general formula C9H11N2O4SR that are produced by molds (genus Penicillium and especially P. notatum or P. chrysogenum) or synthetically and are used especially against gram-positive cocci also : a mixture of such acids

2 : a salt or ester of a penicillin or a mixture of such salts or esters

Examples of penicillin in a Sentence

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Along with flu shots, others that tend to cause stinging and soreness later are tetanus, MMR (measles, mumps and rubella), pneumonia, typhoid, and some antibiotics, like penicillin, Stewart explained. Erica Sweeney, Teen Vogue, "Why Do Some Vaccines Hurt More Than Others?," 24 Oct. 2018 People with certain neurological or cardiac forms of illness may require intravenous treatment with antibiotics such as ceftriaxone or penicillin. Kara Driscoll, ajc, "Lyme disease: 7 questions answered about tick-borne infections," 7 May 2018 That's one of the reasons scarlet fever was a leading cause of heart disease for adults before penicillin was discovered. Meera Senthilingam And Sandee Lamotte, CNN, "Health agency warns UK parents as scarlet fever cases soar," 27 Mar. 2018 At the time, Harris likened the proliferation of medical pot to telling patients to chew on mold instead of taking penicillin. Jenna Portnoy, Washington Post, "D.C.’s biggest pot proselytizer moves to Maryland to take on his nemesis, Rep. Andy Harris," 10 Apr. 2018 Although penicillin could be manufactured fairly easily in the laboratories at the university, many other drugs were not so simple, even with talent and ingenuity. Nan Randall, The Atlantic, "'Charlottesville': A Government-Commissioned Story About Nuclear War," 25 Jan. 2018 But the strain identified at the Orange County facility is more of a superbug, which produces enzymes that can break down a range of antibiotics in the penicillin family. Naseem S. Miller,, "Penicillin-resistant superbug found in Orange County facility, CDC report says," 5 June 2018 Blockbusters including penicillin and statins, which lower cholesterol, came from fungi. Peter Andrey Smith,, "This Fungus Could Help Cure Cancer," 4 June 2018 Fungi are the basis for many drugs, including the antibiotic penicillin, the immunosuppressant cyclosporine and the cholesterol buster lovastatin, so Blanchette wondered if these Antarctic species might produce any useful molecules. Peter Andrey Smith, Scientific American, "Microbes Living in Antarctic Huts Produce Novel Chemical Compounds," 1 June 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'penicillin.' 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 penicillin

1929, in the meaning defined at sense 1

History and Etymology for penicillin

New Latin Penicillium

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19 Nov 2018

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The first known use of penicillin was in 1929

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English Language Learners Definition of penicillin

: a medicine that is used to kill harmful bacteria


pen·​i·​cil·​lin | \ˌpe-nə-ˈsi-lən \

Kids Definition of penicillin

: an antibiotic that is produced by a mold and is used against disease-causing bacteria


pen·​i·​cil·​lin | \ˌpen-ə-ˈsil-ən \

Medical Definition of penicillin 

1 : a mixture of relatively nontoxic antibiotic acids produced especially by molds of the genus Penicillium (as P. notatum or P. chrysogenum) and having a powerful bacteriostatic effect against various chiefly gram-positive bacteria (as staphylococci, gonococci, pneumococci, hemolytic streptococci, or some meningococci)

2 : any of numerous often hygroscopic and unstable amido acids (as penicillin G, penicillin O, and penicillin V) that have a structure in which a four-membered lactam ring shares a nitrogen and a carbon atom with a thiazolidine ring to which it is fused and that are components of the penicillin mixture or are produced biosynthetically by the use of different strains of molds or different media or are synthesized chemically

3 : a salt or ester of a penicillin acid or a mixture of such salts or esters

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More from Merriam-Webster on penicillin

Spanish Central: Translation of penicillin

Nglish: Translation of penicillin for Spanish Speakers Encyclopedia article about penicillin

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