To define functions, let us take a simple example; we know that area of a circle is given by \(\pi {r^2}\), which means that area is dependent on radius \(r\). So area is a function of \(r\) and this can be written as:\[\rm{Area} = f(r)\].Similarly volume of a cuboids is \(abc\), where \(a\), \(b\) and \(c\) are sides of the cuboids. Hence Volume is a function of \(a\), \(b\), \(c\).\[V = f(a, b, c)\]

Where \(a\), \(b\), \(c\) are independent variables and Volume is dependent variable. Hence a function is single-valued relation in dependent and independent variables and the letter \(‘f’\) stands for the first letter of the word function only. We can use some other symbols in place of \(‘f’\) like \(‘g’\), \('\phi '\) etc.