Definition of "reagent" [re•a•gent]

• A substance used in a chemical reaction to detect, measure, examine, or produce other substances. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "The most remarkable feature of Tebbe's reagent is a methylene group bridging between titanium and aluminum, which could replace the oxygen in a carbonyl group in a Wittig-like reaction."
• "The reagent is first reacted with borane (BH3) which can then reduce a carbonyl group to an alcohol."
• "In the reaction shown below only one of the mirror image forms of a Corey-reagent is used."