This article addresses the distinction amongst adpositions between those adpositions which are lexical and those which are functional. The article uses a corpus linguistic approach to address outstanding questions: whether there are two distinct subclasses of adposition, whether the distinction is a continuum amongst adpositions, and how— by what properties— lexical and functional adpositions are distinguished. The article argues for a primarily semantic, multifaceted distinction amongst adpositions, best understood as a continuum. The distinction is argued to be quite small, such that lexical and functional adpositions are not strongly differentiated and an argument is made in support of the more functional status of adpositions generally. A “bottom up” approach is used, which builds from the observable differences between two adpositions, one lexical, and one functional, to characterizations about the nature of the lexical versus functional distinction amongst adpositions. The adpositions used as the basis for this approach are Old English ofOE and its present-day English counterpart ofPDE. Of in the history of English offers a uniquely ideal case-study for an investigation into lexical and functional adpositions, given the uncontroversial functional status of ofPDE and the accepted lexical status of ofOE. The article identifies differences between ofOE and ofPDE primarily in semantics, in the number of available semantic relations. Syntax, morphophonology, and the possible replacement of an adposition by case are found not to represent areas of major difference between the adpositions. Instead, there is continuity between the adpositions in syntax and semantics. The historical evidence provides an opportunity to explore the grammaticalization of an adposition from lexical to functional. The comparative findings have consequences for the retention of meaning in semantic expansion and contradict notions of coevolution between syntax and semantics in grammaticalization. The context-specific nature of grammaticalization is also questioned on the basis of the comparison between the adpositions.