Periodic Functions
Periodic functions are functions that repeat over and over for a specific period. More specifically, a function is periodic if there exists some number T>0 such that f(x)=f(x+T) for all possible values of x.
One common example of this is the tangent function, which has a period of \pi.
Non Periodic Functions
Non periodic functions are functions for which there exists no T>0 such that f(x)=f(x+T) for all possible values of x.
A simple example of this is y=x
For any $ T \not=0, x+T \not= x $ for any $ x $
