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

Recent Examples on the Web

Fleming initially struggled to identify the exact strain of the fungus that created the bacteria-free circle in his petri dish, and over the years, several species of Penicillium have been identified as producing penicillin. —Jack Guy, CNN, 2 Oct. 2024

These reactions are similar to those caused by penicillin and may indicate a serious allergy.5 Sulfonamides Sulfonamides, commonly known as sulfa drugs, are a group of antibiotics used to treat various bacterial infections. —Sarah Jividen, Verywell Health, 12 Sep. 2024

Antibiotic resistance Sir Alexander Fleming shared the 1945 Nobel Prize in medicine with Ernst Chain and Sir Edward Florey for the discovery of penicillin and its application in curing bacterial infections. —Meg Tirrell, CNN, 13 Oct. 2024

The resulting Nobel Prizes have since been awarded to the discoverers of penicillin, X-rays, and the structure of DNA—and, as of today, to two scientists who, decades ago, laid the foundations for modern artificial intelligence. —Matteo Wong, The Atlantic, 8 Oct. 2024

Word History

Etymology

New Latin Penicillium

First Known Use

1929, in the meaning defined at sense 1

Kids 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