Page 308 - English - Teaching Academic Esl Writing

294 CHAPTER 11
Prepositions Versus Conjunctions
According to Quirk et al. (1985), sentence and discourse functions of prepo- sitions (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 prep- ositions 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 (see chap. 5 for nominalizations and gerunds). Thus, if the constructions fol- lowing 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 preposi- tion in a prepositional phrase.
after
as
before
Preposition
Conjunction
Preposition
Conjunction
Preposition
Conjunction
After a large-scale disaster, life begins to recolonize the site.
[no verb]
After a large-scale disaster occurs, life begins to recolonize the site, [verb—occurs]
A few hardy pioneer species invade the environment as a start.
[no verb]
As the environment begins to renew itself, afew hardy pioneer species invade the site, [verb—begins]
Before the restoration of the ecosystems,the pioneer species change the soil, [no verb]
Before theecosystemscanberestored,thepioneerspecieschange the soil, [verb phrase—can be restored]
Distinguishing Prepositions and Conjunctions with Identical Forms
3
one)and/orand/or(because/orhelovedhiscountry), butthelatterofthetwointhesepairsisrare.
Other identical forms of prepositions and conjunctions include but and but (except allbut
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