Periodic Function

Periodic functions are functions that return the same to the same $ y $ value after a given interval $ T $ and keeps repeating itself for every increment of $ T $. An example would be:

$ y(t) = 2 cos(2*pi*t) $

where $ y(t) = 1 $ for every full second.

Non-period Function

Non-periodic functions are functions that do not return to the same value after a given interval. An example for this would be:

$ y(t) = t^3 $.