In library classification we use symbols to denote subjects. The names of subjects are in ordinary language understandable to an ordinary person. Therefore, we call it the natural language which comes naturally to the human being living in a society. On the other handthe symbols that we may use to denote a subject, say B, or 510, or QA for mathematics, are artificial in the sense that the common man will not ordinarily understand the meaning of these symbols. Hence these are artificial and intelligible to a specifically trained class of professionals. Their value is only ordinal, which means that these symbols have no quantitative or qualitative value; they only determine the sequence/order of documents on the shelves. These symbols also maintain/preserve the chosen sequence as the books will be replaced at their proper place after taking them out for reading or lending. These symbols do not indicate anything except the order/sequence of these documents on the shelves.