Norm is defined as: "A rule or authoritative standard: a model, a typical example." It is a changed form of the latin "norma," a builder's rule or square, being thus allied to the word normal. It has been used about seventy-five years by mathematicians, who employed "norms" to simplify some of the problems of higher algebra. It has been adopted in law, a norm being a typical case that implies a certain judgment and, by comparison with which other cases, not exactly like it, could be judged. Norms, standard units, have also been recognized in some departments of biology. The expectation of life at any age, and the average length of life for the whole community, are norms, worked out mathematically for life insurance companies by general averages.
Other such averages, that serve as norms, are the pulse rate, used for two thousand years, its relations to number of respirations: