Diagram of simple filtration: oversize particles in the feed cannot pass through the lattice structure of the filter, while fluid and small particles pass through, becoming filtrate.
An odd function can be identified by replacing both the x and y values with -x and -y values. If the values in your equation are the opposite (positives are negatives and negatives are positives), then the function is odd. Take, for example, this equation y = x^2.
An even number is an integer of the form, where is an integer. The even numbers are therefore ..., , , 0, 2, 4, 6, 8, 10, ... (OEIS A005843). Since the even numbers are integrally divisible by two, the congruence holds for even.