We are all aware of the mathematical meaning of functions. for example a function like y=f(x) means that the value of y is dependent on the value of x. if x changes so does y, implying that x is an independent variable, whereas y is dependent. So can the same relation be established between the speed and torque of an I.C engine ? at different speeds, the engine torque varies, so would it be correct to say that engine torque is a function of engine speed. besides the torque v.s speed curve of an I.C engine is also bound to have an equation.