reaction English · revision 3741

+ {{infobox|confidence=established|formation=derivation, calque|attested=1585|origins=la agō}}

+

+ ==Pronunciation==

+ * IPA: /riˈæk.ʃᵊn/^(Roach et al. 2011)

+

+ ==Etymology==

+ It is formed from [[re-]] and [[action]],^(Etymonline) on the model of [[fr|réaction]] and older Italian reattione,^(Etymonline) which are from [[la-med|reāctiō|t=reaction]] (accusative reāctiōnem),^(Etymonline)^(MWU 2024)^(NODE 1998) a noun of action formed in Late Latin from the past participle of [[m|la|reagere|t=to react]], from [[m|la|re-|t=back]] and [[m|la|agere|t=to do, perform]].^(Etymonline)^(MWU 2024) It is related to [[react]] and [[act]].^(Etymonline)^(NODE 1998)

+

+ ==Earliest recorded meaning==

+ Resistance exerted by a body against the impact of another: 1644 in the OED,^(OED 1989) and the 1640s in Etymonline, as action in resistance or response to another action or power.^(Etymonline) Merriam-Webster dates the word to 1585.^(MWU 2024) It was originally a word of physics and dynamics.^(Etymonline)

+

+ ==Semantic evolution==

+ The influence a thing acted upon exerts in return is from 1771.^(OED 1989) In chemistry, the mutual action of substances upon each other, it is from 1836,^(Etymonline)^(OED 1989) and the return of an opposite physical state, as of heat after cold, from 1805.^(OED 1989) The bodily response to a stimulus is from 1896,^(OED 1989) and in psychology a measurable response from 1887,^(OED 1989) with ''reaction time'' from 1874.^(Etymonline) The general sense, a response or feeling caused by an event or statement, is from 1914.^(Etymonline)^(OED 1989) In politics it means opposition to progress or reform, extreme conservatism.^(AHD)^(COED 2004)

+

+ ==Timeline==

+ * 1585 – first known use.^(MWU 2024)

+ * 1644 – resistance of a body.^(OED 1989)

+ * 1771 – reciprocal influence.^(OED 1989)

+ * 1836 – chemical reaction.^(Etymonline)^(OED 1989)

+ * 1874 – ''reaction time''.^(Etymonline)

+ * 1896 – bodily response to a stimulus.^(OED 1989)

+ * 1914 – a general response.^(Etymonline)^(OED 1989)

+

+ ==Modern meaning==

+ ===Noun===

+ # A response to a [[stimulus]] or event.^(AHD)^(MW Collegiate)

+ # A reverse or opposing action.^(AHD)^(MW Collegiate)

+ # Opposition to political or social progress; extreme [[conservatism]].^(AHD)^(MW Collegiate)

+ # In chemistry, a process in which substances interact to form new ones.^(AHD)^(MW Collegiate)

+ # In physics, the equal and opposite force exerted in response to another.^(AHD)^(MW Collegiate)

+ # A bodily response, especially an [[allergy|alt=allergic]] one, to a drug or substance.^(AHD)^(MW Collegiate)

+

+ ==Word family==

+ * [[reactional]]

+ * [[reactionally]]

+

+ ==Related words==

+ * [[react]]

+ * [[reactant]]

+ * [[reactionary]]

+ * [[reactor]]

+ * [[act]]

+ * [[reagent]]

+

+ ==References==

+ {{reflist}}