dictionaries, as to which combinations are analysed as complex prepositions and which as sequences of adverb + preposition. For example, owing to and out of are listed as prepositions, but according to, because of, and instead of are treated as adverb + preposition. Modern descriptive grammars have tended to extend the category of complex prepositions, and there is accordingly some variation in dictionary practice, depending on how far they are influenced by such work. CGEL generally argues against a complex preposition analysis, and favours a "layered head analysis" for expressions like in front of the car. In this analysis, in front is a PP, which is head of a larger PP that has of the car as a complement. Fronting and stranding Preposition fronting (see ) and stranding can occur when the complement PP is an interrogative or relative pronoun, as in the following examples. Fronting Preposition fronting is a feature of very formal registers and rare in casual registers. Not just the interrogative phrase but the PP containing it is fronted. In the example above, the PP with whom is not in its usual position inside the VP after the head verb. Instead, it appear at the front of the clause. When the pronoun is who the accusative whom form is typically used. Stranding In preposition stranding, the relative or interrogative phrase appears at the front of the clause instead of in its usual position inside the P after the head preposition. The preposition is then "stranded", typically at the end of the clause. Semantics Space and time Prepositions most typically denote relations in space and time. Location Prepositions like in and at typically denote locations in space (e.g., I live in Toronto) and time (e.g., I arrived in January). These prepositions often locate something relative to the object (e.g., the speaker relative to Toronto). Goal and source Prepositions like to and from typically denote the beginning or end point of a path in space (e.g., I went from Ottawa to Toronto) and time (e.g., I lived there from 1992 to 2003). Path Prepositions like through and over typically denote the course of a path in space (e.g., I went over the hill) and time (e.g., I lived there through the 1990s). Other The semantic classification of prepositions has no principled limit. But a small sample of the variation can be presented. Because and since are connected to reasons.