A graphical representation of the exponential rate at which radioactive disintegration occurs (see radioactive decay). If half the parent nuclide remains after one time increment, one-quarter will remain after the next (identical) time increment, and so on. A plot of the surviving parent atoms against time in half-lives (see decay constant) gives a decay curve that approaches the zero line asymptotically. In theory it should never attain zero. The number of surviving parent atoms N_(t) at the end of a number of half-lives (n) is simply N_o/2ⁿ. Plotted as a function of time t, survivors form a characteristic decay curve, the equation of which is N_t = N_oe^−λ‎t, where e = 2.718 and λ‎ is the decay constant.