Etymograph

English

reaction

Reaction comes from Old French reaction, from Latin reāctiō, from reagō ‘to react’, from re- ‘again’ + agō ‘to act, drive’.

  1. Proto-Indo-Europeanc. 4500–2500 BCE*h₂eǵ-1‘to drive’reconstructed
  2. Proto-Indo-Europeanc. 4500–2500 BCE*h₂éǵeti1‘to be driving’reconstructed
  3. Proto-Italicc. 1500–700 BCE*agō1‘to drive’reconstructed
  4. Latinc. 75 BCE–200 CEagō2‘to do, act’
  5. Latinc. 75 BCE–200 CEreagō2‘to act upon again; to react’
  6. Latinc. 75 BCE–200 CEreāctiō2‘reaction’
  7. Old Frenchc. 842–1400reaction2
  8. Middle Englishc. 1150–1500reaccion2
  9. Englishearliest quotation 1962reaction2

attested reconstructed ? uncertain or disputed deepest recorded ancestor

  1. 1 Wiktionary, Latin ago
  2. 2 Wiktionary, English reaction
  3. Earliest quotation in Wiktionary’s entry: 1962, Eric Hobsbawm, The Age of Revolution. 1789-1848: “And as Europe advanced year by year more deeply…”.

Lineage

  1. Proto-Indo-Europeanc. 4500–2500 BCE*h₂eǵ-Wiktionary, Latin ago‘to drive’reconstructed
  2. Proto-Indo-Europeanc. 4500–2500 BCE*h₂éǵetiWiktionary, Latin ago‘to be driving’reconstructed
  3. Proto-Italicc. 1500–700 BCE*agōWiktionary, Latin ago‘to drive’reconstructed
  4. Latinc. 75 BCE–200 CEagōWiktionary, English reaction‘to do, act’
  5. Latinc. 75 BCE–200 CEreagōWiktionary, English reaction‘to act upon again; to react’
  6. Latinc. 75 BCE–200 CEreāctiōWiktionary, English reaction‘reaction’
  7. Old Frenchc. 842–1400reactionWiktionary, English reaction
  8. Middle Englishc. 1150–1500reaccionWiktionary, English reaction
  9. Englishearliest quotation 1962reactionWiktionary, English reaction. Earliest quotation in Wiktionary’s entry: 1962, Eric Hobsbawm, The Age of Revolution. 1789-1848: “And as Europe advanced year by year more deeply…”

Word family

English words that share an ancestor with reaction, grouped by the ancestor they share, most familiar first.

through Proto-Indo-European *h₂eǵ- ‘to drive’

  • suggest ← suggestus ← sub ← *supo ← *upó
  • register ← registrum ← regesta ← regerō ← gerō
  • essay
  • gesture ← gestūra ← gerō ← *gezō
  • digest ← digesten ← dīgestus ← dīgerō ← gerō
  • acre ← æcer ← *akr ← *akraz ← *h₂éǵros
  • agrarian ← agrarien ← agrārius ← ager ← *agros
  • congestion ← congestioun ← congestĭō ← congerō ← gerō
  • belligerent ← belligerans ← belligerō ← belliger ← bellum
  • progesterone ← ketone ← Keton ← gestō ← gerō
  • ingest ← ingerō ← gerō ← *gezō
  • agitate ← agitat

460 more relatives in the full family tree

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Today it means

noun An action or statement in response to a stimulus or other event.

Sources

Sources: Wiktionary, “reaction”; the older steps come from the Wiktionary entry for Latin ago. By Wiktionary contributors, CC BY-SA 4.0, via kaikki.org (dump of Oct 3 2026); text adapted and restructured. Language periods are conventional ranges, not dates for this word. License.

Etymograph / Proto-Indo-European *h₂eǵ- / reaction