Traditional grammars define prepositions as “words that indicate a relationship to another word.” Prepositional phrases consist of a preposition plus another word, phrase, or clause that functions as the prepositional complement.
In grammar, a prepositional phrase head is the word that functions as the head of the prepositional phrase. Only prepositions can function as prepositional phrase heads. Examples of prepositions as prepositional phrase heads include the following:
- with the big green hat
- for me
- about that you want a new car
- after twelve minutes
- beneath a rock or boulder
- versus God
- towards a better solution for energy efficiency
- ten years ago*
*Prepositions that follow the prepositional complement are more accurately described as postpositional complements followed by a postposition. Both prepositions and postpositions belong to the category of adposition.
Brinton, Laurel J. & Donna M. Brinton. 2010. The linguistic structure of Modern English, 2nd edn. Amsterdam: John Benjamins Publishing Company.
Hopper, Paul J. 1999. A short course in grammar. New York: W. W. Norton & Company.
Huddleston, Rodney. 1984. Introduction to the grammar of English. Cambridge: Cambridge University Press.