Time-domain is a term used to describe the analysis of mathematical functions, or real-life signals, with respect to time. In the time-domain, the signal or function's value is known at various discrete time points; or for all real numbers, for the case of continuous time.
<math>\frac{\partial x}{\partial t} = v<math> is a common formula for instantaneous velocity where the velocity (v) is calculated as the length of the path (x) derived in the time domain (t).
