Reaction may refer to a process or to a response to an action, event, or exposure:

Physics and chemistry

Chemical reaction A chemical reaction is a process that leads to the IUPAC nomenclature for organic transformations, chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the pos ...

Nuclear reaction In nuclear physics and nuclear chemistry, a nuclear reaction is a process in which two atomic nucleus, nuclei, or a nucleus and an external subatomic particle, collide to produce one or more new nuclides. Thus, a nuclear reaction must cause a t ...

Reaction (physics) As described by the third of Newton's laws of motion of classical mechanics, all forces occur in pairs such that if one object exerts a force on another object, then the second object exerts an equal and opposite reaction force on the first. The th ...

, as defined by Newton's third law *

Chain reaction (disambiguation) A chain reaction in chemistry or physics is a sequence of reactions where a reactive product or by-product causes additional reactions to take place. Chain reaction or The Chain reaction may also refer to: Media * Chain Reaction (game show), ''Ch ...

Biology and medicine

Adverse drug reaction An adverse drug reaction (ADR) is a harmful, unintended result caused by taking medication. ADRs may occur following a single dose or prolonged administration of a drug or result from the combination of two or more drugs. The meaning of this term ...

Allergic reaction Allergies, also known as allergic diseases, refer a number of conditions caused by the hypersensitivity of the immune system to typically harmless substances in the environment. These diseases include hay fever, food allergies, atopic derma ...

Reflex In biology, a reflex, or reflex action, is an involuntary, unplanned sequence or action and nearly instantaneous response to a stimulus. Reflexes are found with varying levels of complexity in organisms with a nervous system. A reflex occurs ...

, neural reaction *

Hypersensitivity Hypersensitivity (also called hypersensitivity reaction or intolerance) refers to undesirable reactions produced by the normal immune system, including allergies and autoimmunity. They are usually referred to as an over-reaction of the immune s ...

, immune reaction *

Intolerance (disambiguation) Intolerance may refer to: * Hypersensitivity or intolerance, undesirable reactions produced by the immune system * Intolerance (film), ''Intolerance'' (film), a 1916 film by D. W. Griffith * Intolerance (album), ''Intolerance'' (album), the first ...

Light reaction (disambiguation) Light reaction may refer to: * Light-dependent reactions * Pupillary light reflex The pupillary light reflex (PLR) or photopupillary reflex is a reflex that controls the diameter of the pupil, in response to the intensity (luminance) of light tha ...

Psychology

Emotion Emotions are mental states brought on by neurophysiological changes, variously associated with thoughts, feelings, behavioral responses, and a degree of pleasure or displeasure. There is currently no scientific consensus on a definition. ...

al, reaction *

Reactivity (behaviour) Proactivity or proactive behavior refers to self-initiated behavior that endeavours to solve a problem before it has occurred. Proactive behavior involves acting in advance of a future situation, rather than reacting. It refers to taking control o ...

Proactivity Proactivity or proactive behavior refers to self-initiated behavior that endeavours to solve a problem before it has occurred. Proactive behavior involves acting in advance of a future situation, rather than reacting. It refers to taking control o ...

, opposite of reactive behaviour *

Reactive attachment disorder Reactive attachment disorder (RAD) is described in clinical literature as a severe and relatively uncommon disorder that can affect children, although these issues do occasionally persist into adulthood.DSM-IV-TR (2000) American Psychiatric Ass ...

Politics and culture

Reactionary In political science, a reactionary or a reactionist is a person who holds political views that favor a return to the ''status quo ante'', the previous political state of society, which that person believes possessed positive characteristics abse ...

, a political tendency *

Reaction video A reaction video is a video in which people react to something. Videos showing the emotional reactions of people viewing television series episodes, film trailers and music videos are also numerous and popular on video hosting services such as You ...

Commentary (disambiguation) Commentary or commentaries may refer to: Publications * ''Commentary'' (magazine), a U.S. public affairs journal, founded in 1945 and formerly published by the American Jewish Committee * Caesar's Commentaries (disambiguation), a number of works ...

Proper names and titles

* ''Reaction'' (album), a 1986 album by American R&B singer Rebbie Jackson ** "Reaction" (song), the title song from the Rebbie Jackson album *"Reaction", a single by

Dead Letter Circus Dead Letter Circus are an Australian alternative rock band from Brisbane, Queensland. Their 2010 debut album ''This Is the Warning'' debuted at No. 2 on the Australian album charts and spawned a number of singles that were played heavily o ...

ReAction GUI ReAction GUI is the widget toolkit engine that is used in AmigaOS 3.2-4.1. It is an evolution of ClassAct, which is an object-oriented system of classes that enhanced the aspect of the Workbench 2.0 GUI of AmigaOS. History The native Amiga win ...

, a GUI toolkit used on AmigaOS *

Reaction.life Reaction.life is a British news website that features reporting and analysis on politics, economics, culture and ideas. Reaction is based in London and edited by former ''Scotsman'', ''Telegraph'' and ''Wall Street Journal'' executive Iain Mar ...

, a political news and commentary website edited by Iain Martin *

Reaction Records Reaction Records was an independent British record label, run by music executive Robert Stigwood in 1966 and 1967. Although Reaction released only three albums, one EP and eighteen singles in its brief existence, its roster included two of the ...

, a record label *''

TNA Reaction ''TNA Reaction'' is an American professional wrestling-focused documentary-style television program by Total Nonstop Action Wrestling (TNA) that aired in the United States and Canada on Spike. The show aired two pilot episodes and a twenty-episod ...

'', a former documentary show of TNA Wrestling (now known as Impact Wrestling) behind the scenes * Reaction (''The Spectacular Spider-Man''), an episode of the American animated television series ''The Spectacular Spider-Man'' *''

The Reaction ''The Reaction'' is the 12th book in the ''Animorphs'' series, written by K.A. Applegate. It is narrated by Rachel. Plot summary At the zoo, Rachel and Cassie witness a boy fall into the crocodile pit. Rachel jumps into the pit to rescue him ...

'', a novel in the ''Animorphs'' series *'' ''Reactions'' (journal), a chemistry journal published by MDPI

Physics and chemistry

Biology and medicine

Psychology

Politics and culture

Proper names and titles

See also