語體是言語活動和語法體系交互作用產生的語言形式變異，不過以往的語體研究還沒有全面關照語法體系對語體變異的制約。本文根據William Croft (2001)提出的激進構式語法，論述基本文篇是先秦語法體系中的定型構式，就此展開語體結構與分類乃至語體和文體之別的討論。本文認為言語活動中的語言形式變異是使用條件在基本文篇的結構框架下形塑出來的，而高層的語體類型可以按照基本文篇類型劃分。如議論語體是以評議文篇為框架的高層語體，它的下位分支因於使用條件而有不同的分類結果，類別之間互有關聯。語體源自語法的規約，文體則是語體的應用， 本文最後解說文體乃至其修辭性變體如何從語體繁衍出來。

Linguistic register is a product of language use through the interaction of speech activities and grammatical systems. Previous studies of pre-Qin Chinese grammar have yet to address the constraints of the grammatical system on register variations. Based on radical construction grammar proposed by William Croft (2001), this paper suggests four basic discourse types within the grammatical system which serve as a structural framework for register variations used in speech activities. Each discourse type corresponds to certain grammatical forms in one respect, and to register variations in another. Register variations are shaped by use conditions under the structural framework of basic discourse types and can be classified according to use conditions. For example, argumentative variations share the comment type as their structural framework and can be subclassified according to use conditions such as communicative purposes and the relative social status between interlocutors. The difference of linguistic register and style is as follows: linguistic register is rooted from the grammatical system, whereas style is the application of linguistic register. The present paper concludes by elucidating how styles and their rhetoric variants are derived from register variations.