as a complement are called conjunctive prepositions or subordinating prepositions. Conjunctive prepositions can take a variety of kinds of clauses as complements. Most often, they take finite clauses as complements. These finite clause complements can be declarative (this happened after Stacy left) or interrogative (they ignored the question of whether it was ethical). They can also be subjunctive clauses (lest there be any doubt). Less commonly, conjunctive prepositions take non-finite clauses as complements. These non-finite clause complements include infinitive clauses (we can't agree on how much to charge) and present participle clauses (you can't just put it on without them knowing). These clauses may occur with or without subjects, and subjects that do occur can be in accusative case (without them knowing) or genitive case (without their knowing). Though various usage commentators have called both cases incorrect in such clauses, many writers use both constructions, and the choice of case often depends on the context. For example, the accusative case is more likely when the subject is emphasized, a phrase intervenes between the subject and the verb, or the subject is plural. Other complements of prepositions In more limited cases, prepositions can take other kinds of complements. The preposition as can take an adjective phrase complement to form a prepositional phrase that functions as an object complement (you described them as jealous). Prepositions also take adjective phrase complements in certain fixed phrases, such as at last and in brief. As with adjective phrase complements, prepositions can take adverb phase complements in fixed phrases, such as by far and since when. Further, certain prepositions (namely, before/ere, for, and till/until) can take temporal adverbs (such as later, long, one, and recently) as complements, forming prepositional phrases such as for later, until recently, for once, and before long. Prepositions can also take prepositional phrases as complements. These prepositional phrase complements can be specified by the preposition or not. In the prepositional phrase apart from Jill, for example, the preposition apart requires that the complement include the preposition from. In the prepositional phrase since before the war, however, the preposition since does not require the preposition before and could have instead been something else, such as since after the war. Modifiers of prepositions Prepositions may optionally be modified by other phrasal categories. Adverb phrases, noun phrases, and prepositional phrases can function as pre-head modifiers of prepositions (that is, modify prepositions that follow them), and