Reaction

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Reaction might refer to:

• In chemistry, an interaction involving one or more substances that results in a change to their molecular or ionic structure, releasing or consuming energy
• In geology, a process during metamorphism where a group of minerals transforms into different minerals that are more thermodynamically stable in the new heat/pressure conditions
• In politics, a reactionary
• In physics, the description of all forces having reactions opposite to the action
• In pseudophysics, a claim for perpetual motion that there can exist a reactionless thruster
• In psychology, a Freudian term, the defense mechanism known as the reaction formation
• A form of YouTube content that involves a streamer watching another video with their audience, interspersing it with their own commentary. HasanAbi is one famous reaction streamer, and reaction content often has concerns with plagiarism and copyright