Time domain is the analysis of mathematical
functions, physical
signals or
time series of
economic or
environmental data, with respect to
time. In the time domain, the signal or function's value is known for all
real numbers, for the case of
continuous time, or at various separate instants in the case of
discrete time. An
oscilloscope is a tool commonly used to visualize real-world signals in the time domain. A time-domain graph shows how a signal changes with time, whereas a frequency-domain graph shows how much of the signal lies within each given frequency band over a range of frequencies.