Definition of "reactant" [reactant]

• A substance participating in a chemical reaction, especially a directly reacting substance present at the initiation of the reaction. (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.

• "One prototype he likes uses thorium as the reactant, which is 3-4 times more abundant than uranium and produces several orders of magnitude less long-lived radioactive waste."
• "In current research we are developing a method for simultaneous measurement of three or four vector properties of reactive collisions, such as reactant or product relative velocities or rotational angular momenta."
• ""What kind of reactant is Quent Miles using in that ship of yours?" asked Walters sharply."