Language as a system is also closely interwoven with other aspects of man and society. It has often been studied in ways that relate linguistics to other disciplines. A number of hybrid disciplines have propped up since 1960s.

　 Sociolinguistics studies language in relation to society. Language varies from region to region, from class to class, and it also varies with age and sex. Language changes are mostly caused by social changes. Language is part of culture and the carrier of culture. Language variations and the relation between language and culture will also be discussed in Chapter 8.

　 Psycholinguistics deals with the relation between language and mind. How speech is produced and comprehended? How language is acquired? How do people learn a second/foreign language? What are the similarities and differences between first language acquisition and second language acquisition? All these questions are explored in psycholinguistics. Major findings about and theories of second language acquisition will be introduced in Chapter 9.

　 Applied linguistics is concerned with the application of linguistic theories and descriptions in other fields, particularly in language teaching. Chapter 10 will show what roles linguistics plays in the whole process of language teaching as part of formal education.