The prepositional phrase consists of a preposition followed by a prepositional complement (or object, in more traditional terms). The complement is usually a noun phrase, but can also be an -ing participle clause or wh- clause, e.g.:
Prepositions can be simple or complex. Complex prepositions consist of more than one word, and generally can be divided into three categories:
adverb + preposition: along with, apart from, aside from, as for, away from, etc.
verb, adjective, conjunction, etc. + preposition: except for, owing to, due to, but for, because of, etc.
preposition + noun + preposition: by means of, in comparison with, instead of
Prepositional phrases can function as adverbials, postmodifiers of nouns or adjectives or verb complements, e.g.:
He lost his hat on the train (adverbia1)
The hat with the green feather is pretty (noun postmodifier)
He's happy about his promotion (adjective postmodifier)
He's looking for his hat (verb complement)
In the case of prepositional phrases functioning as verb complements, there are a number of complicated semantic and syntactic criteria that can be used to determine the degree to which the preposition belongs more to the verb or to the following complement, but these need not concern us here (cf. Quirk et al. 1972: §12.19 ff.).
The two sections which follow describe errors involving the choice of prepositional complement (4-1) and of preposition (4.2).