penicillin
noun
pen·i·cil·lin
ˌpe-nə-ˈsi-lən 
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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Policies protecting research participants grew out of revelations in the early 1970s about the Tuskegee Syphilis Study, in which poor African American men in a syphilis study were not told about a penicillin cure.
—
Lisa M. Krieger, The Mercury News, 29 Jan. 2025
In general, penicillins and cephalosporins are considered safe during pregnancy.
—Erika Prouty, Verywell Health, 4 Oct. 2024
Doxycycline lowers the effectiveness of penicillins.
—Megan Nunn, Verywell Health, 22 Jan. 2025
Over 90 percent of antibiotics that are currently in use are derived from nature in some way, including the life-saving penicillin.
—Laura Baisas, Popular Science, 22 Jan. 2025
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Lisa M. Krieger, The Mercury News, 29 Jan. 2025
In general, penicillins and cephalosporins are considered safe during pregnancy.
—Erika Prouty, Verywell Health, 4 Oct. 2024
Doxycycline lowers the effectiveness of penicillins.
—Megan Nunn, Verywell Health, 22 Jan. 2025
Over 90 percent of antibiotics that are currently in use are derived from nature in some way, including the life-saving penicillin.
—Laura Baisas, Popular Science, 22 Jan. 2025
See All Example Sentences for penicillin
Cite this Entry
“Penicillin.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/penicillin. Accessed 28 Feb. 2025.
Copy CitationKids Definition
penicillin
noun
pen·i·cil·lin
ˌpen-ə-ˈsil-ən
: any of several antibiotics or a mixture of these produced by penicillia or in the laboratory and used especially against round disease-producing bacteria
Etymology
from scientific Latin Penicillium "a genus of molds producing antibiotics," from Latin penicillus, literally, "little tail" — related to pencil
Medical Definition
penicillin
noun
pen·i·cil·lin
ˌpen-ə-ˈsil-ən
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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