[ me-thahy-uh-neen, -nin ]
/ mɛˈθaɪ əˌnin, -nɪn /

noun Biochemistry.

an amino acid, CH3SCH2CH2CH(NH2)COOH, found in casein, wool, and other proteins or prepared synthetically: used as a supplement to a special diet in the prevention and treatment of certain liver diseases. Abbreviation: Met; Symbol: M

Origin of methionine

1925–30; blend of methyl and thionine Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

British Dictionary definitions for methionine


/ (mɛˈθaɪəˌniːn, -ˌnaɪn) /


an essential amino acid containing sulphur, which occurs in many proteins: important in methylating reactions

Word Origin for methionine

C20: meth- + thionine
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Medicine definitions for methionine


[ mə-thīə-nēn′ ]


A sulfur-containing essential amino acid obtained from various proteins or prepared synthetically and used as a dietary supplement and in pharmaceuticals.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Science definitions for methionine


[ mə-thīə-nēn′ ]

An essential amino acid. Chemical formula: C5H11NO2S. See more at amino acid.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.