The object of this paper is to show that the preposition instead of can take a greater variety of grammatical categories for its complement than the other prepositions chiefly taking a noun phrase, a gerund, and/or a wh-clause for their complements. It is also to explore what makes it possible for this preposition to do so. We have found out that it is structurally different from the other prepositions in that it has the property of coordinateness and joins A and B coordinately in the string A instead of B, just as a coordinator links the conjuncts of the same grammatical category. This study argues that this makes it possible for instead of to take more various types of grammatical categories for its complements than the other prepositions. It also makes the category of B predictable from that of A and vice versa. Based on this point we refer to the preposition instead of as a coordinate preposition.