It is represented by o. All waves including sound. As an example of the distinction and the relatedness of frequency and period consider a woodpecker that drums upon a tree at a periodic rate.
The relationship between frequency and period is f 1 T f 1 T.
If you set the time standard to years the period is 1365 years while the frequency is 365 cycles per year. For a given pendulum the time period is the same every time. The formula for angular frequency is the oscillation frequency f measured in oscillations per second multiplied by the angle through which the body moves. Therefore frequency is inversely proportional to period.