1.NounIn a radioactive material, an atom's probability, per unit time, of decaying; it is related to half-life by the equation
t
1
/
2
=
ln
2
λ
{\displaystyle t_{1/2}={\frac {\ln 2}{\lambda }}}
, where
t
1
/
2
{\displaystyle t_{1/2}}
is the half-life, and
λ
{\displaystyle {\lambda }}
is the decay constant.