Aspects of varieties differentiation

There has been much discussion of intra-lingual varieties in recent years. Catford has pertinently stated the problem which has prompted this discussion and justified the need to solve it (1965:83): ‘The concept of a “whole language” is so vast and heterogeneous that it is not operationally useful for many linguistic purposes, descriptive, comparative and pedagogical. It is therefore desirable to have a framework of categories for the classification of “sub-languages” or varieties within a total language.’