1712, "repercussive, echoing," a sense now obsolete, from react + -ive. By 1822 as "caused by a reaction;" 1888 as "susceptible to (chemical) reaction." Related: Reactively; reactiveness; reactivity.
Entries linking to reactive
react v.
1640s, "to exert, as a thing acted upon, an opposite action upon the agent," from re- "back" + act (v.). Related: Reacted; reacting (1610s). For sense development, see reaction. The verb meaning "to perform again, do a second time" (often written re-act and given full pronunciation of the prefix to distinguish it from react) is from 1650s, from the "again" sense in re-.
-ive
word-forming element making adjectives from verbs, meaning "pertaining to, tending to; doing, serving to do," in some cases from Old French -if, but usually directly from Latin adjectival suffix -ivus (source also of Italian and Spanish -ivo). In some words borrowed from French at an early date it has been reduced to -y (as in hasty, tardy).
proactive adj.
also pro-active, of persons or policies, as an opposition to reactive, "taking the initiative in a situation, anticipating events" as opposed to responding to them, 1921, from pro- + active. From 1933, in psychology (learning theory). Related: Proactively; proactiveness; proactivity.