Periodic Function
Periodic function of CT is $ y(t)=sin(t) $. Proof: $ y(t+T)= sin(t+T) $,where we take $ T=2*pi $.
so $ sin(t+T)=sin(t+2*pi)=sin(t) $ i.e $ y(t+T)=y(t) $. so it's periodic function.
Non-Periodic Function
Non-periodic function is $ y(t)=t $. Proof: assume y(t) is periodic, then there exists a non-zero T,that makes$ y(t+T)=y(t) $
i.e. $ t+T=t $,so $ T=0 $,which violates the assumption. So $ y(t)=t $ is a non-periodic function