Define the terms time period and frequency of an oscillating body. Give their units and write the relation between them. 

Time period: The time taken by an oscillating body to complete one oscillation is called its time period.

It is denoted by T.

SI unit of time period is second (s).

Frequency: The number of oscillations or vibrations completed by an oscillating body in one second is called its frequency.

Frequency is symbolically denoted by v (Greek letter nu).

SI unit of frequency = per  socond (s^-1)

                               = cycles per second (cps)

                               = hertz |(Hz.)


Relation between time period and frequency:

Let T be the time period of an oscillating body.

Then number of oscillations completed in T second = 1

So, number of oscillations completed in 1 second =$\frac{1}{\mathrm{T}}$

But frequecny($\mathrm{\nu }$) is the number of oscillations completed in 1 second.

Therefore, $\mathrm{\nu }$ = $\frac{1}{\mathrm{T}}$ 

Hence, number of oscillations is equal to the recoprocal of time period.