What is the average and marginal product of an input?

Marginal product refers to the change or difference in the total product when additional input is employed, assuming other inputs are constant. Suppose to produce an output only two factors of production labour and capital are employed then an increase in labour that is

MP_L = Δ TP_L/ΔL

Average product refers to the average output produced per input used. Mathematically it is represented as:

AP_L = TP_L/L