What are the social functions of language?

In cognitive and psychological theories, we often treat Language (note the use of the capital letter L to distinguish universal, internal grammar from particular instances of language) as a specialised mental faculty with a potential of generating infinite utterances from finite means or as an elegant system that can help communicate unstructured ideas and thoughts in a neat, structured way. However, a complete theory of Language will be one that incorporates the social dimension of language use. We cannot look at Language as a completely self-contained system (Malinowski). There are things external to Language, such as society, which have a major role to play in structuring and shaping a language. In fact, it is difficult to study language and communication in isolation. The area of linguistics that deals with social functions of language governed by different social factors is known as Sociolinguistics. Social factors often provide context of language use, which are dealt separately in another area of linguistics known as Pragmatics. The social functions of language take into account social factors like gender, social status, age, education, geographical background, ethnicity, etc. of the language user. For example, there are studies that show the presence of marked differences in the speech style of men and women. The speakers of a language take into consideration all these social factors while communicating with other speakers. Hence, while expressing ideas, a man will use different language strategies with a senior or boss (strictly formal), with a colleague (comparatively less formal), with a friend or sibling (informal) and with his wife (intimate). Social dimension of language is necessary for effective interaction with other language speakers.