The concept of socio-linguistics ultimately implies a ʻsocio-semanticsʼ which is a genuine meeting ground of two ideologies, the social and the linguistic. And this faces both ways. The options in meaning are significant linguistically because selections in grammar and vocabulary can be explained as a realization of them. They are significant sociologically because they provide insight into patterns of behaviour that are in turn explainable as realizations of the pragmatic and symbolic acts that are the expressions of the social structure.
- Halliday (1973), Pag. 64-65

In sociological linguistics we are interested in that part of language behaviour which CAN be related to social factors and stated in these terms. We examine areas which are relatively circumscribed; and we select those which are of intrinsic interest–-noting at the same time, however, that the investigation of the socio-linguistic interface may also shed valuable light on the nature of language itself.
- Halliday (1973), Pag. 83

In sociological linguistics the interest is in linguistic as well as in social phenomena, and so we need to explore areas of behaviour where the meanings are expressed through very general features, features which are involved in nearly all uses of language, such as transitivity in the clause.
- Halliday (1973), Pag. 84