reactive

/riˈæktɪv/

/riˈæktɪv/

Other forms: reactively

To be reactive is to be ready to react or respond to something else — as opposed to ready to act on one's own. A person who's reactive does things only in response to others.

To react is to do something in response to something else. When someone pinches you, for example, you react. But if you're a reactive person, then you only react; you're always ready to react but not to act on your own. You're rather lifeless unless something or someone else causes you to do act. This is usually seen as a negative trait in people, unless you're talking about, say, firefighters or cops. We admire people who don't need prodding to get things done. Some chemicals are called reactive, too, because they react readily with other chemicals.

Definitions of reactive

1. adjective

   participating readily in reactions
   “sodium is a reactive metal”

   “free radicals are very reactive”

   synonyms:

   activated, excited

   (of e.g. a molecule) made reactive or more reactive

   labile

   (chemistry, physics, biology) readily undergoing change or breakdown

   oxidizable

   capable of undergoing a chemical reaction with oxygen

   thermolabile

   (chemistry, physics, biology) readily changed or destroyed by heat

   unstable

   highly or violently reactive

   antonyms:

   unreactive

   (chemistry) not reacting chemically

   inactive

   (chemistry) not participating in a chemical reaction; chemically inert

   indifferent, inert, neutral

   having only a limited ability to react chemically; chemically inactive

   noble

   inert especially toward oxygen

   stable

   not taking part readily in chemical change
2. adjective

   reacting to a stimulus
   “the skin of old persons is less reactive than that of younger persons”

   synonyms: responsive

   sensitive

   responsive to physical stimuli