Complex prepositions

In general, the syntactic function of prepositions is to express a relationship between two entities; in this way they are similar to coordinating conjunctions and sentence transitions, which mark a relationship between ideas in two sentences. Complex prepositions are those that consist of more than word-usually of two or three words (e.g., as for, except for, in line with).

Prepositions Versus Conjunctions

According to Quirk et al. (1985), sentence and discourse functions of prepositions (and complex prepositions as a subclass) have much in common with those of conjunctions and adverbs. Both prepositions and conjunctions have connecting functions:

the time when Ireland experienced a population crash in 1845
the time of a population crash in Ireland in 1845
the time of the 1845 population crash in Ireland
the time of the 1845 Irish population crash

In fact many prepositions and conjunctions have identical forms and, for this reason, can be confusing for learners (e.g., after, as, before, since, until). The key difference between conjunctions and prepositions is that prepositions are always followed by a noun, noun phrase, or nominalizations, including gerunds, but conjunctions conjoin the main and subordinate clauses, which necessarily have the predicate verb or verb phrase. Thus, if the constructions following such words as after or before contain a verb, this sentence unit is a subordinate clause. If no verb can be identified, the word is the preposition in a prepositional phrase.

Distinguishing Prepositions and Conjunctions with Identical Forms
after	preposition	After a large-scale disaster, life begins to recolonize the site. [no verb]
	conjunction	After a large-scale disaster occurs, life begins to recolonize the site. [verb-occurs]
as	preposition	A few hardy pioneer species invade the environment as a start. [no verb]
	conjunction	As the environment begins to renew itself, a few hardy pioneer species invade the site. [verb-begins]
before	preposition	Before the restoration of the ecosystems, the pioneer species change the soil. [no verb]
	conjunction	Before the ecosystems can be restored, the pioneer species change the soil. [verb phrase-can be restored]
since	preposition	Since the 1960s, the urban growth has declined. [no verb]
	conjunction	Since suburbs began to attract urban residents, a large number of jobs also shifted to smaller cities. [verb phrase-began to attract]
till/until	preposition	Until the expansion of suburban job markets, most urban dwellers lived in central cities. [no verb]
	conjunction	Until manufacturing job markets emerged in the early 1800s, only 5% of Americans lived, in cities. [verb-emerged]

In addition to simple (one-word) prepositions and conjunctions with identical forms, many complex prepositions and subordinating conjunctions also have similar meanings and text functions. In academic writing, some can be used interchangeably provided that verbs are not included in constructions following complex prepositions.

Complex Prepositions

Complex prepositions can be divided into two groups: two-word and three-word units. They are relatively easy to identify:

• Two-word prepositions consist of a word + a simple preposition.
• Three-word sequences include a simple preposition + a Noun + a simple preposition.

The uses of complex prepositions, in addition to sentence transitions and subordinate conjunctions in complex sentences, can provide writers with a large number of options among lexical connectors. However, as with sentence transitions, the mere usage of connectives of any type does not serve to make disjointed text cohesive. Many two- and three-word prepositions have similar connective functions and can be used in proximate syntactic constructions. In addition, the meanings of complex prepositions are also similar to those of sentence connectives such as transitions and subordinators. Various constructions with the connective functions can be used interchangeably provided that the syntactic constructions they conjoin are modified accordingly (e.g., only nouns and noun phrases can be used following prepositions, and whole clauses after sentence transitions and subordinators in complex sentences). For example:

• In spite of [preposition] such local and regional disasters [noun phrase], the overall human population on earth has continued to grow.
• Despite [preposition] joblessness and overcrowding [noun phrase], shantytown residents cling to life with resourcefulness, tenacity, and hope.
• * Nevertheless/However [transition], municipal governments do not strive to improve the quality of life for new urban arrivals. Not only lacking the money, officials also fear that improving services will attract even more of the rural poor.
• Although/Even though [subordinator] disease is rampant in the squalor [adverb clause], most urban migrants do have more opportunities and are better off than the rural poor they left behind.

Most Common Two- and Three-Word Prepositions and Their Substitutions

Two-Word Prepositions	Three-Word Prepositions and Substitutions
according to	Prepositions, etc.: in accordance with, in line with, based on
ahead of	Prepositions: in front of (place), prior to (time) Preposition/Transition: before (place/time)
along with, aside from, together with	Prepositions: in addition to Transitions: also, further
because of, due to	Subordinators: because, since Transitions: therefore, as a result, so
contrary to	Transitions: however, on the other hand, on the contrary, in contrast to/with
except for	Prepositions: apart from, aside from, with the exception of
instead of	Prepositions: in lieu of, in place of
prior to	Prepositions and Subordinators: before (time), until
subsequent to	Prepositions: after, following
Most Common Three-Word Prepositions and Their Substitutions
by means of	Preposition: with (instruments/tools only)
in (the) case of	Subordinators: if, as long as, unless, provided that
in (the) process of	Preposition: during Subordinators: while, when Transitions: meanwhile,in the meantime
in spite of	Preposition: despite Subordinators: though, although, even though Transition: nevertheless
in view of, in light of	Preposition: due to

As many teachers know from experience, a common tendency among L2 writers is to employ a particular set of connectives repeatedly in their text (e.g., according to, moreover, therefore). However, the quality of academic writing is often evaluated based on lexical and syntactic variety, and providing writers with options for essential academic expressions may help create less stilted prose (Davidson, 1991; Hale et al., 1996; Read, 2000). To this end the usage of complex prepositions in addition to sentence transitions and subordinate clauses can provide at least some degree of variation among lexical connectives and syntactic structures.