The logical product of two or more logical sum terms is known as a product of sums expression. POS is an ANDing of ORed variables. The boolean expression containing all the input variables either in complemented or un complemented form in each of the sum term is known as a canonical POS expression and each term is called maxterm. For example, express the product of sum from the boolean function F(X, Y) and the truth table for which is given below:
| X | Y | F | Maxterm |
| 0 | 0 | 1 | X+Y |
| 0 | 1 | 0 | X+Y’ |
| 1 | 0 | 0 | X’+Y |
| 1 | 1 | 1 | X’+Y’ |
Now by multiplying max terms for the output 0’*, we get the desired product of sums expression which is (X+Y') (X’+Y).
