There is a half-life describing any exponential-decay process. For example:
*As noted above, in radioactive decay the half-life is the length of time after which there is a 50% chance that an atom will have undergone nuclear decay. It varies depending on the atom type and isotope, and is usually determined experimentally. See List of nuclides.
*The current flowing through an RC circuit or RL circuit decays with a half-life of  or , respectively. For this example the term half time tends to be used rather than "half-life", but they mean the same thing.
*In a chemical reaction, the half-life of a species is the time it takes for the concentration of that substance to fall to half of its initial value. In a first-order reaction the half-life of the reactant is , where  (also denoted as ) is the reaction rate constant.