the act or an instance of reacting
a mental or emotional response to circumstances
a bodily response to a stimulus, e.g. the response of tissues to a foreign substance, e.g. a drug or an infective agent
tendency towards a former and usu outmoded political or social order or policy
a chemical transformation or change; specif an action between atoms, molecules, etc to form one or more new substances
a process involving change in atomic nuclei resulting from interaction with a particle or another nucleus
in physics, the force that something subjected to the action of a force exerts equally in the opposite direction
reactionist noun and adj