Cohesion Theory And Its Applications In College English Teaching

M.A.K Halliday, a founder of systemic-functional school of linguistics, proposes three"metafunctions"of language—the ideational, the interpersonal and the textual function. Ideational function is realized by the system of transitivity and voice. Interpersonal function is achieved by the system of mood, modality and appraisal. Textual function is represented by the system of thematic structure, information structure and cohesion.The concept of cohesion was first put forward by M.A.K Halliday and R. Hasan in 1964. They state that, semantically, cohesion exists not only grammatically within the sentence structure, but also links larger chunks of text and classify cohesion into five categories: reference, substitution, ellipsis, conjunction and lexical cohesion.Grammatical cohesion is a kind of surface marking of semantic links between clauses and sentences in written texts and utterances and it falls into four categories: reference, substitution, ellipsis and conjunction. Reference is a device which allows the receiver to trace participants, entities, events etc. in a text. There are three types of reference: personal, demonstrative and comparative. Substitution refers to the replacement of one item by another, usually, for the purpose of reducing redundancy. The three types of substitution are nominal, verbal and clausal. Ellipsis can be defined as substitution by zero. When something that is structurally necessary is left unsaid, ellipsis occurs. It is divided into nominal, verbal and clausal ellipsis. Conjunction expresses certain meanings that presuppose the presence of other components in a discourse.Lexical cohesion is obtained through lexis or vocabulary. There are two types of lexical cohesion: reiteration and collocation.Cohesive patterns play an indispensable role in the process of text by a listener or a reader. They signal organizational patterns of texts. The knowledge of cohesion theory encourages students to make great efforts to read and search for needed messages and contributes to their awareness of different ways referring to the discourse so that they know what to choose in a certain text, therefore, their text creating and decoding abilities can be improved.