n. The state of being reactive: the process or course of reaction, as from a diseased condition.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. responsive to stimulation
n. ready susceptibility to chemical change
Word Usage
"This high reactivity is of direct importance for the catalytic activity of the enzyme, but Moore and Stein also found it possible to utilize it to label two amino acids in the active site by chemical modification."