中文摘要：

以认知语言学的语义理论为依据，以英国国家语料库收集到的语料为基础，通过比较近义介词over和above在“高于”这一意义上的用法，探索多义介词词义拓展中的认知机制。对于两者在“高于”这个意义层面上相对比较全面的分析，为介词意义的理据性提供证明。介词意义之间的关系不是孤立的，存在从空间域到抽象域的隐喻拓展，而这种拓展可能，是与人类的身体体验密切相关的。这对于语言教学中的词义区分、词汇记忆以及字典的编撰和语义研究都具有积极的意义。

英文摘要：

Based on the semantic theory of cognitive linguistics and data collected from British National Corpus, the paper explores the motivation in the meaning extension of polysemous prepositions by making a relatively comprehensive comparison between above and over in the aspect of ＂being higher than＂. The result shows that metaphorical usages of the two prepositions are decided by their spatial usages, and the meaning extension is closely related with our bodily experiT- ences. The result proves that there is motivation in the meaning extension of prepositions and is meaningful for lexical teaching, dictionary compilation and semantic study.