This essay is showing an opinion that despite the many disadvantages of T.G grammar,its main theories about human language learning can give valuable guide to language teaching,which will be illustrated in the following from three main aspects.
Language deviation means that language users can use language forms that are different from conventional ones toachieve a better communication function of language, that is, the expressive effects they expect. And the expressive effects of thederivated language forms sometimes are unique, that is, they cannot be achieved by the conventional language forms. This phenom-enon also reflects that the internal meaning of language external forms is unlimited. This essay tries to study the expressive effectsof language deviation and explore the internal meaning of the external language form, so that language users can express their mean-ings and convey their feelings more concisely with a creation in the external language form, which also will give people a sense ofbeauty through with its odd appearance.