Abstract: Variation is one of the essential features of language. It exists in all the levels of linguistic system and thus linguistic theories must include the explanation on linguistic variation. Fruits of the early variation research mainly were concentrated on the part of sound system, while little progress on syntactic variation is achieved. A methodological problem preventing the variationists from probing into higher level syntactic variation further is the definition of a sociolingusitic variable. With a case study of have to, have got to, and got to, this paper proposes a new criterion to identify a syntactic variable, namely, only when they are equivalent in meaning will the different variants constitute a syntactic variable. 

Key words: syntactic variation; syntactic variable; variants; semantic criterion

摘要：变异是语言的本质性特征，存在于语言系统的各个层级，因而语言学理论必须包括对语言变异的解释。社会语言学关于语言变异的研究成果主要集中在音系领域，句法变异研究一直以来没有太大的进展。其中一个主要的障碍在于句法变项确立标准的莫衷一是。本文以have to, have got to和got to变异为例，探讨了语言变异的定义扩展问题，在整合前人提出的有关标准的基础上,提出了“语义”标准，对句法变项加以确定。本文的研究期望在句法变异研究方面产生一些积极的意义。

关键词：句法变异；句法变项；变式; 语义标准