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Medical Term:

first-order reaction


Definition: a reaction in which the rate is proportional to the concentration of the single substance undergoing change; radioactive decay is a first-order process, defined by the equation dN/dt = kN, where N is the number of atoms subject to decay (reaction), t is time, and k is the first-order decay (reaction) constant, the fraction of all atoms decaying per unit of time.

See Also: decay constant, order

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