Etymologically
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reactive

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Pronunciation

  • UK: /ɹiːˈæktɪv/[1]
  • US: /ɹiˈæktɪv/[1]

Etymology

It is formed from English react + -ive.[2][3][4][5] The chemical sense may follow French réactif, recorded in that sense from 1740, and the rare noun use follows the French noun.[2][4] Merriam-Webster instead suggests an assumed New Latin reactivus, from reagere (“to react”).[6] react itself is formed from re- and act.[3][2]

Earliest recorded meaning

Acting in return or in response: 1649, in Charleton's translation of van Helmont.[2]

Semantic evolution

Blackmore used it in 1712 for "echoing, repercussive", a sense that soon died out, and in 1717 for exerting a physical reaction.[2][3] The chemical sense, apt to react with other substances, is recorded from 1803 in the OED and 1888 in Etymonline,[2][3] and in medicine and physiology the word described a response to a stimulus from 1894.[2] Psychiatry used it from 1900 for a mental illness caused by an outside event, as reactive depression.[2][7][6] Since 1927 it has also described a person or organization that responds to events instead of anticipating them, the opposite of proactive.[2][7] In electricity it relates to reactance.[7][6][4]

Timeline

  • 1649 – acting in response.[2]
  • 1712 – echoing (obsolete by 1733).[2][3]
  • 1717 – exerting a physical reaction.[2]
  • 1803 – tending to react chemically.[2]
  • 1894 – showing a physiological reaction to a stimulus.[2]
  • 1900 – of a mental illness, caused by outside events.[2]
  • 1927 – responding to events rather than anticipating them.[2]

Meanings

Adjective

  1. Readily taking part in chemical reactions: Potassium is highly reactive in water.[7][2][4]
  2. Responding to a stimulus.[7][6][2]
  3. Tending to react to events rather than plan ahead or start change: a reactive approach to safety.[7][2]
  4. Of a mental illness, caused by stress or an outside event: reactive depression.[7][6][2]
  5. Of or relating to reactance.[7][6]

Word family

  • reactively
  • reactiveness
  • reactivity
  • antireactive
  • hyperreactive
  • immunoreactive
  • nonreactive
  • overreactive

References

  1. ^ a b Wiktionary, the free dictionary, https://en.wiktionary.org
  2. ^ a b c d e f g h i j k l m n o p q r s t Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
  3. ^ a b c d e Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
  4. ^ a b c d Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
  5. ^ Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
  6. ^ a b c d e f Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
  7. ^ a b c d e f g h Collins English Dictionary (2023), Glasgow: HarperCollins