Integers can be represented on a number line as whole numbers. These include 0 and counting back from zero: -1, -2, -3 and so on, as well as counting forward: 1, 2, 3 and so on. In algebra, quite often an integer is represent by the letter n. So n is a number which has no fractional part. On a ruler or tape measure the integers are the main marked divisions. (All rational fractions are the result of dividing one integer by another (but not zero)).