What does a prepositional phrase always have?

In most cases, a proper prepositional phrase must contain both the phrase itself and a complement, an additional Word or phrase that immediately follws the prepositional phrase.

Complements are typically one of three things:

1. noun phrase - the most common complement. Ideas such as on the table or under the bridge feature a noun phrase complement.
2. adjective phrase - Ideas like on fireor for granted. It can also work with the preposition "as" as a what's called a predicative compliment: Joe's attempt to save the puppy was seen as honorable
3. adverb phrase - These complements are rare, and they are generally found in common phrases, such as before long.

Complements generally occur AFTER the proposition - a long time ago is one example of an exception. It is also possible for prepositions to complement prepositions, but, even in that case, the phrase would still contain a dedicated preposition and complement combination.