(iii) The textual function

　 In using language, we organize messages in a logical way so that they fit in with the other messages and with the wider context in which we are talking or writing. When we speak or write we usually don't confine ourselves to single phrases or sentences; we string them together to form a text. There are expressions that refer backwards and forwards, or substitute for others, or link phrases or sentences. They play the role of bringing units of language into unity.