1An action performed or a feeling experienced in response to a situation or event.

嘉丽的第一反应是感到宽慰。

1. 1.1reactions A person's ability to respond physically and mentally to external stimuli.
   （人对外部刺激的）反应力
   a skilled driver with quick reactions

   反应极快的熟练驾驶员。

   Example sentencesExamples

   • You will soon develop quicker reactions and a sixth sense for when someone is going to do something unorthodox.
   • The driver's reactions and abilities wouldn't enter into it.
   • Thus, we consider that birds actually reacted to both stimuli, but reactions were probably weaker than tests performed the previous year.
   • The drink he had had would have affected his judgement, ability to ride and reactions.
   • Likewise, neuroticism may be linked not with stronger reactions to negative stimuli, but with weaker reactions to positive stimuli.
2. 1.2 An adverse physiological response to a substance that has been breathed in, ingested, or touched.
   （对吸入、咽下或触及的东西的）不良生理反应
   such allergic reactions as hay fever and asthma

   干草热和哮喘等过敏反应。

   Example sentencesExamples

   • Rarely, skin tests can produce a severe, immediate allergic reaction.
   • Anaphylactic reactions have been seen most often after multiple administrations of thiamine.
   • "Each antibiotic medicine can cause a strong adverse drug reaction.
   • Hypersensitivity reactions have also occurred with lamotrigine therapy; some reactions have been fatal or life-threatening.
   • Aside from mild gastrointestinal distress and allergic reactions, side effects are rare, and serious toxicity rarely has been reported.
   • The mechanism for these adverse muscle reactions is unknown.
   • In the realm of immunology, substances that cause immune responses or allergic reactions are known as antigens.
   • Increased awareness of adverse drug reactions can assist the clinician in differential diagnosis of medical problems and events.
   • Pharmacological and therapeutic measures also may be applied to limit adverse physiological reactions to GMA.
   • Rock found that exposure to dogs increased levels of cytokines, chemicals that dampen the body's reactions to allergens.
   • Other adverse effects of ticlopidine include neutropenia, adverse skin reactions and gastrointestinal side effects.
   • One risk of any such procedure would be the small possibility of an allergic reaction to the anesthetic used.
   • Vaccinia immune globulin is a first-line therapy for certain adverse reactions to smallpox vaccine.
   • Patients with a known anaphylactic hypersensitivity reaction to eggs should not be vaccinated.
   • Other measures that should be performed to minimize the risk of adverse reactions to allergen immunotherapy are listed in Table 6.
   • Vitamin B 1 may cause a hypersensitivity reaction or dermatitis.
   • Twenty-five patients experienced adverse drug reactions, but only 12 of them needed drug modifications.
   • If you don't have an adverse reaction, the allergen dose is increased each time you receive a shot.
   • Patients were reassessed on day 4 of therapy for clinical and laboratory responses and for adverse reactions to the medication.
   • If major adverse reactions occur, the regimen, or the offending drug, if identified, must be stopped.
3. 1.3 A chemical process in which two or more substances act mutually on each other and are changed into different substances, or one substance changes into two or more other substances.
   化学反应
   Example sentencesExamples

   • Chemists study these organisms because they are able to perform chemical reactions under extreme conditions.
   • Equivalents can be used to simplify balancing chemical equations for many reactions.
   • Filler metal is obtained from an exothermic reaction between iron oxide and aluminum.
   • The chemical equations for some reactions may have a lone reactant or a single product.
   • Exothermic reactions involve the production of energy which is given to the surrounding environment as heat.
   • Three randomly picked clones from each PCR reaction were eventually sequenced.
   • Such " ribozymes " are often used to catalyze reactions involving deoxyribonucleic acid or RNA.
   • By contrast, making Kevlar involves a complex series of organic reactions in hot sulphuric acid at high pressures.
   • The rate of a photolysis reaction is a first-order process.
   • Indeed, electrical currents could lead to a potential drop and to heating and catalysis of undesirable electrochemical reactions.
   • Many of these vinyl compounds are made by the reaction of acetylene with electrophiles.
   • There are many important industrial processes that use electrophilic reactions.
   • These materials are based on the polymerization reaction of a diol with a diisocyanate.
   • Zeolites can soak up liquid or gas molecules and also catalyze chemical reactions.
   • One of the primary methods of qualitative analysis involves precipitation reactions.
   • Alkylation reactions are reactions where an alkyl group is introduced into a molecule.
   • It is formed from the reaction of nitric oxide with superoxide, and produces carbonyls on proteins.
   • Ozone is produced when sunlight triggers chemical reactions involving reactive hydrocarbons and nitrogen oxides.
   • Acid reactions are also used in organic synthesis reactions for making polymers, vitamin supplements, and other everyday consumer products.
   • More to the point, it has facilitated many reactions that depend upon acetic acid as a reagent or solvent.
4. 1.4Physics An analogous transformation of atomic nuclei or other particles.
   〔物理〕反应
   Example sentencesExamples

   • They're produced during nuclear fusion, the reaction that lights the sun and other stars.
   • Cold fusion is the term proposed to describe controlled nuclear fusion reactions occurring at or near room temperature.
   • Furthermore, the compound nuclei produced in cold-fusion reactions contain a relatively small number of neutrons.
   • Nucleophilic substitution reactions can be either unimolecular or bimolecular.
   • It studies the structure of nuclei, and their reactions and interactions.
5. 1.5 A mode of thinking or behaving that is deliberately different from previous modes of thought and behavior.
   反抗；对抗
   the work of these painters was a reaction against fauvism

   这些画家的作品是对野兽派的对抗。

   Example sentencesExamples

   • Europhobia seems to be more a reaction against anti-Americanism and its theoretical foundations.
   • But in general there was a strong reaction against the excesses of the previous age.
   • It is heartening to see a reaction against modern society's safety-first attitude towards child-rearing.
   • I think this tendency is a reaction against previous generations' parenting styles.
   • And if the public has a big reaction against something, the story's going to stay for a while.
   • The reaction against the neo-brutalism of the 1960s and 1970s was to embrace safe conformism instead.
   • In the film, Richard goes native as a reaction against the West.
   • Was this a reaction against this supermarket/microwave culture?
   • So a book Cain wrote as a reaction against his crime novellas became a combination of thriller and woman's picture - film noir.
   • What's driving the British reaction against Guantanamo Bay?
   • The rise of conservative views, clubs, and newspapers is a direct reaction against being told how to think.
   • But among the younger generation there has been a reaction against the positivist and analytical traditions.
   • The World Bank was actually born in this era of state-led development - it was the Keynesian reaction against the free market.
   • There was then a reaction against these positions.
   • And in all its forms, even on the conservative Right, it is a reaction against the Enlightenment and is thus essentially new.
   • Mawo started in January of 2002 as a reaction against aggressive war behavior of the United States.
   • It is a reaction against modern R & B, which is neither drearily excessive nor underachieving.
   • But we're now seeing a reaction against mass production in the renaissance of organic farming and farmers' markets.
   • This is as much a critical reaction against contemporary Hollywood as it is an attempt to capture early-Fifties America.
   • The reaction against raves reflects familiar anxieties about what the kids are up to, especially when it comes to sex.

   Synonyms

   backlash, counteraction, recoil
6. 1.6 Opposition to political or social progress or reform.
   反动，极端保守主义
   the institution is under threat from the forces of reaction

   这一机构受到反动势力的威胁。

   Example sentencesExamples

   • It was the forces of reaction which were most prominent and most successful in the 1960s.
   • This process of social and political reaction cannot be adequately explained as the result of the evil intentions of one or another president.
   • To find a social base for its reactionary agenda, big business is invariably forced to cultivate political reaction and cultural backwardness.
   • He was to become a bookseller and publisher as well as the owner and editor of the Political Register, in which he launched shattering onslaughts against the forces of reaction.
   • The fight against war and social reaction requires a socialist perspective.
   • The Catholic church may well be a force for intolerance and reaction.
   • The mood of the broad masses is quite at odds with the creed of avarice and social reaction that animates the incoming government.
   • It is bound up entirely with the underlying program of militarism abroad and social reaction at home.
   • When you talk about working in a rights mode there is always the element of reaction and pressure.
   • Ngugi was a professor of English literature at the University of Nairobi until the forces of reaction forced him to flee from Kenya in 1982.
   • American politics has assumed the form of a sweeping social reaction, aimed at overturning the reformist legacy of the New Deal.
   • The White House agenda of militarism and social reaction is not some accident, nor is it merely the whim of certain right-wing individuals.
   • In periods of political reaction, innumerable forms of social backwardness, ignorance and stupidity come into their own.
   • I think Jack makes a very good point - the forces of extreme reaction are anti-intellectual, but also radical, even if they don't realise it.
   • Today, the Labour Party is a bastion of political reaction.
   • Such a position ignores the real roots of militarism, war and social reaction - the crisis of American and world capitalism.
   • The latter had pledged to sweep all traces of Zionism, imperialism and the forces of reaction in the Arab world.
   • It is no coincidence that this development has occurred during a period of deepening social and political reaction.
   • The forces of reaction in Europe rallied against what they took to be the International and all its works.
   • There is no shortcut in the struggle against imperialist war and social reaction.

   Synonyms

   conservatism, ultra-conservatism, the right, the right wing, the extreme right
7. 1.7Physics Repulsion or resistance exerted in opposition to the impact or pressure of another body; a force equal and opposite to the force giving rise to it.
   〔物理〕反作用（力），反力，阻力
   Example sentencesExamples

   • At the same time, the centrifugal forces of interest and reaction caused local people to reconceive the boundaries of their nation.
   • Newton's third law states that for every action there's an equal and opposite reaction.
   • In response to the motion, the elastic reaction force exerted on the site by the substrate starts to rise.