Definition of reaction in English:



  • 1Something done, felt, or thought in response to a situation or event.

    ‘my immediate reaction was one of relief’
    [mass noun] ‘prices fell in reaction to intense competition’
    • ‘We are appreciative of the Australian government's reaction to the situation.’
    • ‘He acknowledged that he had an immediate gut reaction to government requests for the media to withhold information.’
    • ‘We need to stop worrying about what others think of us and make pictures that elicit a gut reaction.’
    • ‘The violence of Violet's reaction had not surprised her, indeed, she was rather pleased by it.’
    • ‘Yet the fear of this technical underworld has provoked a knee-jerk reaction.’
    • ‘Describing her mother's reaction to the news, Harrold said she was unable to face even her closest friends.’
    • ‘However, people have very different mental responses to the body's natural reaction to a stressful situation.’
    • ‘Negative emotional reactions are often caused by stress.’
    • ‘He said he has been surprised by the positive reaction from the public.’
    • ‘We test whether the market's reaction to such announcements differs among different types of units relocated.’
    • ‘And with little change in Fed thinking, the financial markets' reaction was muted.’
    • ‘Are you surprised by the reaction of your fans?’
    • ‘The mention of Thomas provoked an immediate reaction from Becky as the Shopkeeper knew it would.’
    • ‘I accept full responsibility for my reaction to a bad situation.’
    • ‘The market's reaction was swift and brutal.’
    • ‘We also observe a positive market reaction to the announcements of relocations involving corporate headquarters and plants.’
    • ‘And for an immediate reaction to today's events I think we can speak to Tom Hilton.’
    • ‘Of course, that explained Mother's reaction to the news and her respectfully mournful look.’
    • ‘Fifth, anger can be an immediate reaction to an isolated event or it can be a response after numerous events.’
    • ‘The only people who usually benefit from a knee-jerk emotional reaction to a security event are the vendors.’
    1. 1.1A person's ability to respond physically and mentally to external stimuli.
      ‘a skilled driver with quick reactions’
      • ‘You will soon develop quicker reactions and a sixth sense for when someone is going to do something unorthodox.’
      • ‘The drink he had had would have affected his judgement, ability to ride and reactions.’
      • ‘The driver's reactions and abilities wouldn't enter into it.’
      • ‘Likewise, neuroticism may be linked not with stronger reactions to negative stimuli, but with weaker reactions to positive stimuli.’
      • ‘Thus, we consider that birds actually reacted to both stimuli, but reactions were probably weaker than tests performed the previous year.’
    2. 1.2An adverse physiological response to a substance that has been breathed in, ingested, or touched.
      ‘such allergic reactions as hay fever and asthma’
      • ‘Other measures that should be performed to minimize the risk of adverse reactions to allergen immunotherapy are listed in Table 6.’
      • ‘One risk of any such procedure would be the small possibility of an allergic reaction to the anesthetic used.’
      • ‘Rock found that exposure to dogs increased levels of cytokines, chemicals that dampen the body's reactions to allergens.’
      • ‘Patients with a known anaphylactic hypersensitivity reaction to eggs should not be vaccinated.’
      • ‘Aside from mild gastrointestinal distress and allergic reactions, side effects are rare, and serious toxicity rarely has been reported.’
      • ‘If major adverse reactions occur, the regimen, or the offending drug, if identified, must be stopped.’
      • ‘Rarely, skin tests can produce a severe, immediate allergic reaction.’
      • ‘Vaccinia immune globulin is a first-line therapy for certain adverse reactions to smallpox vaccine.’
      • ‘Increased awareness of adverse drug reactions can assist the clinician in differential diagnosis of medical problems and events.’
      • ‘Twenty-five patients experienced adverse drug reactions, but only 12 of them needed drug modifications.’
      • ‘Patients were reassessed on day 4 of therapy for clinical and laboratory responses and for adverse reactions to the medication.’
      • ‘In the realm of immunology, substances that cause immune responses or allergic reactions are known as antigens.’
      • ‘Pharmacological and therapeutic measures also may be applied to limit adverse physiological reactions to GMA.’
      • ‘The mechanism for these adverse muscle reactions is unknown.’
      • ‘"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.’
      • ‘Other adverse effects of ticlopidine include neutropenia, adverse skin reactions and gastrointestinal side effects.’
      • ‘Vitamin B 1 may cause a hypersensitivity reaction or dermatitis.’
      • ‘Anaphylactic reactions have been seen most often after multiple administrations of thiamine.’
      • ‘If you don't have an adverse reaction, the allergen dose is increased each time you receive a shot.’
    3. 1.3A mode of thinking or behaving that is deliberately different from previous modes of thought and behaviour.
      ‘the work of these painters was a reaction against Fauvism’
      • ‘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.’
      • ‘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.’
      • ‘Was this a reaction against this supermarket/microwave culture?’
      • ‘The reaction against the neo-brutalism of the 1960s and 1970s was to embrace safe conformism instead.’
      • ‘The reaction against raves reflects familiar anxieties about what the kids are up to, especially when it comes to sex.’
      • ‘The World Bank was actually born in this era of state-led development - it was the Keynesian reaction against the free market.’
      • ‘This is as much a critical reaction against contemporary Hollywood as it is an attempt to capture early-Fifties America.’
      • ‘Europhobia seems to be more a reaction against anti-Americanism and its theoretical foundations.’
      • ‘I think this tendency is a reaction against previous generations' parenting styles.’
      • ‘So a book Cain wrote as a reaction against his crime novellas became a combination of thriller and woman's picture - film noir.’
      • ‘But we're now seeing a reaction against mass production in the renaissance of organic farming and farmers' markets.’
      • ‘It is heartening to see a reaction against modern society's safety-first attitude towards child-rearing.’
      • ‘And if the public has a big reaction against something, the story's going to stay for a while.’
      • ‘In the film, Richard goes native as a reaction against the West.’
      • ‘But in general there was a strong reaction against the excesses of the previous age.’
      • ‘There was then a reaction against these positions.’
      • ‘It is a reaction against modern R & B, which is neither drearily excessive nor underachieving.’
      backlash, counteraction, recoil
      View synonyms
    4. 1.4[mass noun]Opposition to political or social progress or reform.
      ‘the institution is under threat from the forces of reaction’
      • ‘Today, the Labour Party is a bastion of political reaction.’
      • ‘There is no shortcut in the struggle against imperialist war and social reaction.’
      • ‘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.’
      • ‘Such a position ignores the real roots of militarism, war and social reaction - the crisis of American and world capitalism.’
      • ‘In periods of political reaction, innumerable forms of social backwardness, ignorance and stupidity come into their own.’
      • ‘It was the forces of reaction which were most prominent and most successful in the 1960s.’
      • ‘The latter had pledged to sweep all traces of Zionism, imperialism and the forces of reaction in the Arab world.’
      • ‘The White House agenda of militarism and social reaction is not some accident, nor is it merely the whim of certain right-wing individuals.’
      • ‘The Catholic church may well be a force for intolerance and reaction.’
      • ‘It is no coincidence that this development has occurred during a period of deepening social and political reaction.’
      • ‘It is bound up entirely with the underlying program of militarism abroad and social reaction at home.’
      • ‘The mood of the broad masses is quite at odds with the creed of avarice and social reaction that animates the incoming government.’
      • ‘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.’
      • ‘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.’
      • ‘When you talk about working in a rights mode there is always the element of reaction and pressure.’
      • ‘The fight against war and social reaction requires a socialist perspective.’
      • ‘American politics has assumed the form of a sweeping social reaction, aimed at overturning the reformist legacy of the New Deal.’
      • ‘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.’
      • ‘The forces of reaction in Europe rallied against what they took to be the International and all its works.’
      conservatism, ultra-conservatism, the right, the right wing, the extreme right
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  • 2A chemical process in which substances act mutually on each other and are changed into different substances, or one substance changes into other substances.

    ‘a chemical reaction caused by a build-up of particular sodium salts’
    • ‘Many of these vinyl compounds are made by the reaction of acetylene with electrophiles.’
    • ‘Three randomly picked clones from each PCR reaction were eventually sequenced.’
    • ‘It is formed from the reaction of nitric oxide with superoxide, and produces carbonyls on proteins.’
    • ‘Indeed, electrical currents could lead to a potential drop and to heating and catalysis of undesirable electrochemical reactions.’
    • ‘Ozone is produced when sunlight triggers chemical reactions involving reactive hydrocarbons and nitrogen oxides.’
    • ‘Zeolites can soak up liquid or gas molecules and also catalyze chemical reactions.’
    • ‘Chemists study these organisms because they are able to perform chemical reactions under extreme conditions.’
    • ‘Such " ribozymes " are often used to catalyze reactions involving deoxyribonucleic acid or RNA.’
    • ‘Filler metal is obtained from an exothermic reaction between iron oxide and aluminum.’
    • ‘More to the point, it has facilitated many reactions that depend upon acetic acid as a reagent or solvent.’
    • ‘There are many important industrial processes that use electrophilic reactions.’
    • ‘The chemical equations for some reactions may have a lone reactant or a single product.’
    • ‘By contrast, making Kevlar involves a complex series of organic reactions in hot sulphuric acid at high pressures.’
    • ‘One of the primary methods of qualitative analysis involves precipitation reactions.’
    • ‘Alkylation reactions are reactions where an alkyl group is introduced into a molecule.’
    • ‘The rate of a photolysis reaction is a first-order process.’
    • ‘These materials are based on the polymerization reaction of a diol with a diisocyanate.’
    • ‘Equivalents can be used to simplify balancing chemical equations for many reactions.’
    • ‘Acid reactions are also used in organic synthesis reactions for making polymers, vitamin supplements, and other everyday consumer products.’
    • ‘Exothermic reactions involve the production of energy which is given to the surrounding environment as heat.’
    1. 2.1Physics An analogous transformation of atomic nuclei or other particles.
      ‘reactions between photons and electrically charged atomic particles’
      • ‘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.’
      • ‘Nucleophilic substitution reactions can be either unimolecular or bimolecular.’
      • ‘It studies the structure of nuclei, and their reactions and interactions.’
      • ‘Furthermore, the compound nuclei produced in cold-fusion reactions contain a relatively small number of neutrons.’
  • 3Physics
    [mass noun] A force exerted in opposition to an applied force.

    ‘the law of action and reaction’
    • ‘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.’


Mid 17th century: from react + -ion, originally suggested by medieval Latin reactio(n-), from react- done again (see react).