2.4.2 Lexis and Grammar

Sinclair prioritizes a method or a way of investigating language by observing large amounts of naturally-occurring computerized texts.The first point involves his objection to the traditional basic language model featured by the separation of grammar and lexis，the two elements by means of which language creates meaning.He introduces the idea that sense and structure，or lexis and grammar，are closely associated and interdependent，and“［t］here is ultimately no distinction between form and meaning”（1991：7）.

The basic assumption is that a certain sense of a word seems to co-select certain syntactic structures in which the word frequently occurs.Seen from the other side of the coin，a certain syntactic structure is most likely to be filled with a limited range of items sharing certain aspects of meaning.Sinclair sees it the self-evident proposition of the present approach to corpus linguistics that“meaning and cotext are co-related”（2004：170），and that the realization of meaning“involves at least partial co-selection”（ibid：170）.As argued by Sinclair，one important feature of lexical structure is its straddling on the“borders between grammar and semantics”；lexis is neither“the residue of a grammatical description”nor“bound by the conventions of grammar”，“but a different way of describing the same events”（ibid：172）.

The co-selection between grammar and lexis leads Sinclair to postulate that“the underlying unit of composition is an integrated sense-structure complex”（1991：105）.In other words，when we want to express a certain idea，we do not choose grammar or lexis independently but choose both combined，or the phrases that have a single form and a single meaning.At this point，Sinclair raises the status of such more-or-less fixed phrases to a kind of idiom and articulates the idiom principle.