| 释义 |
re·action
\rē+\ noun
(-s)
Etymology: New Latin reaction-, reactio, from reactus (past participle of reagere to react) + Latin -ion-, -io -ion — more at react
1.
a. : exertion of reciprocal or counteracting force or influence
< the reaction between an individual and his environment >
b. : action in opposition to some force or influence
< reaction against dictatorship >
c. : movement in or tendency toward a reverse direction : return to a prior condition
< a strong reaction in stock prices >
d. : a tendency toward or movement in support of a former especially outmoded or repressive political or social condition, policy, or form of government
< mixture of sober conservatism, timid standpattism, and angry reaction — Clinton Rossiter >
2.
a. : a particular response to a particular treatment, situation, or other stimulus
< watched her reaction to the news >
b. : bodily response to or activity aroused by a stimulus:
(1) : motor response (as muscular movement or secretion) to stimulation
(2) : the whole sensorimotor process comprising intellectual and emotional elements as well as pure motor response : total response of an organism to a stimulus
c.
(1) : an action induced by vital resistance to some other action
< inflammatory reaction to bacterial infection >
especially : the specific result (as hemolysis, local inflammation, or a rise in bodily temperature) characteristically evoked in cells or tissues or in vitro by a foreign substance and used in various serological tests to determine specific sensitivities or the presence of particular infection
< the tuberculin reaction >
< the precipitin reaction >
< allergic reactions >
(2) : depression or exhaustion of vital force consequent on overexertion or overstimulation
(3) : heightened activity and overaction succeeding depression or shock
(4) : a psychosis, psychoneurosis, or other mental or emotional disorder forming an individual's response to his life situation
< an anxiety reaction >
< a schizophrenic reaction >
3. : the force that a body subjected to the action of a force from another body exerts in the opposite direction
4.
a.
(1) : chemical transformation or change : the reversible or irreversible interaction of molecules, atoms, ions, or radicals to form one or more new substances
< the reaction of acid with base >
< the reaction of hydrogen with oxygen gives water >
< endothermic and exothermic reactions >
— see equation 2b, order of a reaction; compare catalysis, decomposition, polymerization, substitution, synthesis
(2) : the state resulting from such a reaction
< an alkaline reaction >
b. : a process involving change in atomic nuclei (as the disintegration of uranium 239 into neptunium and an electron or the union of heavy-hydrogen nuclei to form helium nuclei) — called also nuclear reaction; compare chain reaction, fission, fusion, spallation
5. : the effect of organisms upon their habitat — compare coaction
6. : the degree of acidity or alkalinity of soil |