Halliday believes that language should deal with meaning, that it is contextualized and culturally situated, a system which allows us to perform tasks. He rejects Chomsky’s philosophical idea of language as pure form, in favor of language as natural. Chomsky and his followers stressed competence, Halliday stresses performance. Language, to Halliday, is a mean of cultural transmission and social interaction. His work on language development in young children illustrates the process by which meanings become words, and words become expressions, and that grammars evolve organically: As the child’s needs become more complex, so does his means of expressing them. Halliday’s work stresses that language is notational (idea) and functional (action.) His work is highly significant for language teachers, and forms the basis for the predominant EFL teaching methodologies: communicative language learning, content based instruction, and the development of functional/notational syllabi.

In CBI, language tasks are taught through content, as opposed to the memorization of grammatical structures. It has great relevance for teachers of EAP, English for Academic Purposes, CIL, Content Integrated Language Learning, which deals with young second language learners in English language classrooms, and ESP, English for Special Purposes, aimed at professionals who need English for their work. In communicative language teaching, language is an action rooted in a social context rather than an abstract system of rules. Communicative Language teaching is rooted in Halliday’s theories, stressing meaning over structure, fluency over accuracy, and communication over rote memorization, a learner centered over a teacher centered classroom. Unlike Chomsky, who asks what language is, Halliday explores what it does: it allows us to express needs, control behavior, interact socially, express feelings, inform and be informed, and most importantly, to learn.