Prepositions indicate a relationship between a noun in a phrase immediately following it and some other noun or verb in the sentence. Often the basic relationship expressed is that of location, but other relations, such as time, possession, part-whole relations, origin, etc., can also be identified, depending on the semantics of the preposition and the nouns associated with it. Rarely does a preposition express only one relationship in every use; translations vary accordingly by context. In this chapter, the most basic and best-known translation will be used for convenience, but any good dictionary will show other possibilities. The object of a preposition is the noun or noun phrase immediately following it; mutation effects and/or case marking of the object noun follow from this closeness. Irish prepositions may be either simple or complex; these will be covered in turn in this chapter.