time constant

time constant (plural time constants)

1. (mathematics) A characteristic of an exponential function, represented by τ in the function:

   ${\displaystyle y(t)\ =\ y_{o}e^{-t/\tau }\ }$.

2. (physics) The time in which a physical system's response to a step-wise change in an external variable reaches approximately 63% of its final (asymptotic) value.
3. For radioactivity: the decay constant.

• time-constant

• constant time