Simple sentences such as The fire glowed and Extremely frigid fall winds chilled my sweater-loving puppy of small stature to his tiny little bones during his bedtime walk in the dark are sentences that contain only one clause. Formed by the noun phrase functioning as the subject The fire and the verb phrase functioning as the predicate glowed, the first example is clearly a simple sentence because the single subject and single predicate form a single clause. As exemplified by the second sentence, however, simple sentences need not be simple in structure nor semantics. Although the second example contains multiple noun phrases functioning as subject and objects and multiple prepositional phrases functioning as complements and adverbials in addition to the verb phrase functioning as the predicate, the sentence still only contains a single subject and a single predicate that form a single clause.
Complex sentences, too, contain a single clause known as the main, independent, superordinate, or matrix clause (Hopper 1999: 212; Quirk et al. 1985: 991). In addition to the main clause, however, complex sentences also contain one or more subordinate or dependent clauses (Hopper 1999: 212; DeCarrico 2000: 142; Quirk et al. 1985: 987). For example, the sentences Because the evening was terribly chilly, we lit a roaring fire and The puppy will sleep through the night assuming he tires himself out are complex because both contain the subordinate clauses Because the evening was terribly chilly and assuming he tires himself out as well as the main clauses we lit a roaring fire and The puppy will sleep through the night. As constituents of the sentence as a whole, subordinate clauses are not arguments of the predicate and therefore not subjects or objects but instead function as modifiers of the entire main clause (Quirk et al. 1985: 987; Jacobs 1995: 66; Hopper 1999: 212). Subordinate clauses can therefore only appear attached to main clauses as in He attended the concert even though he hated the band but not *even though he hated the band or *Because the sky was dark (DeCarrico 2000: 142-143; Jacobs 1995: 66; Justice and Ezell 2002: 217). Subordinate or dependent clauses are thus called because of their subordination to or dependence on the main clause.
Similar to clauses in simple sentences like Apple cider tastes sweet and Clowns terrify children as well as most librarians and main clauses in complex sentences like Lucy will hold the football because Charlie Brown has a signed document and Sally will be angry unless the Great Pumpkin arrives, subordinate clauses must contain both a subject and a predicate (Justice and Ezell 2002: 217). For example, the subordinate clauses in the complex sentences Trees loose their leaves once the weather turns chilly and Although that she hated his mother surprised him, he still allowed her to attend the family dinner contain both subjects and predicates. The subject of the first example is the noun phrase the weather and the subject of the second the noun clause that she hated his mother. The predicate of the first example contains the verb phrase turns and the adjective phrase chilly and the predicate of the second the verb phrase surprised and the noun phrase him. Unlike clauses in simple sentences and main clauses in complex sentences, however, subordinate clauses also contain subordinating conjunctions that precede the subject (O’Dwyer 2000: 200; Jacobs 1995: 67).
Subordinating conjunctions or subordinators are conjunctions that introduce subordinate clauses (DeCarrico 2000: 143). For example, the lest in the complex sentence Linus always waits in a sincere pumpkin patch lest he miss the Great Pumpkin and the considering in Considering he bravely flew during battle, Snoopy is a great World War I Flying Ace introduce the subordinate clauses lest he miss the Great Pumpkin and Considering he flew bravely during battle; lest and considering are therefore examples of subordinating conjunctions. Bernard O’Dwyer (2000) identifies the functional potential of subordinating conjunctions as connecting subordinate clauses to main clauses as in the subordinating conjunction because connecting the subordinate clause his daddy dropped it to the main clause The puppy ate the pea in the complex sentence The puppy ate the pea because his daddy dropped it (201). Similar to other grammatical categories such as sentences and prepositions, subordinating conjunctions differ in form as either simple or complex. Simple subordinating conjunctions, which are the most prototypical subordinating conjunctions in the English language, consist of one word such as although, because, once, since, unless, whereas, and while (Quirk et al. 1985: 998; O’Dwyer 2000: 98-99). For instance, the complex sentence Although I would like to go to bed early, I must finish my essay first contains the simple subordinating conjunction although.
Unlike simple subordinating conjunctions, complex subordinating conjunctions are periphrastic consisting of multiple words as in in that, assuming that, provided that, except that, insofar as, and as though (Quirk et al. 1985: 998). Within the complex category, subordinating conjunctions obligatorily end with that as in in that and in the event that, obligatorily end with as as in as soon as and insofar as, optionally end with that as in so that or so and given that or given, or fall into a small category of other complex subordinating conjunctions as in as though and in case (Quirk et al. 1985: 998). Many subordinating conjunctions optionally ending with that resemble participles and some prepositions in form as in considering that or considering and provided that or provided but are distinguished from other forms by the following clause (Quirk et al. 1985: 998). For example, the subordinating conjunction considering is distinguished from the preposition considering in the examples Considering my brother ate the entire pie, we will not be having dessert tonight and You will write a detailed essay considering the topic by the clause my brother ate the entire pie following the subordinating conjunction and the noun phrase the topic following the preposition.
Subordinate clauses that begin with subordinating conjunctions such as because and assuming that in sentences like Her house was freezing because the furnace broke and Assuming that you carefully follow my directions, you should arrive in less than five hours are termed adverb clauses. Adverb clauses function similarly to other adverbials, which are broadly defined as phrases that express time, place, manner, condition, reason, or purpose of a clause (O’Dwyer 2000: 200; Hopper 1999: 67, 256; Justice and Ezell 2002: 220; DeCarrico 2000: 143). For example, the prepositional phrase because of the fierce winter storm functions as an adverbial to the clause The university closed for an entire week in the sentence The university closed for an entire week because of the fierce winter storm by expressing the reason for the occurrence of the main clause (Hopper 1999: 119). The prepositional phrase because of the fierce winter storm describes the reason for which the entire clause occurred. Subordinate clauses functioning as adverb clauses also modify the entire main clause to which the subordinate clause is attached (DeCarrico 2000: 143). In the complex sentence The university closed for an entire week because the fierce storm completely covered the roads with snow, the subordinate clause functioning as an adverb clause because the fierce storm completely covered the roads with snow again expresses the reason for the occurrence of the main clause. In other words, the proposition of the subordinate clause is the reason for the proposition of the main clause. Just as the prepositional phrase functioning as an adverbial because of the fierce storm modifies the main clause The university closed for an entire week, the subordinate clause functioning as an adverb clause because the fierce storm completely covered the roads with snow modifies the other main clause The university closed for an entire week.
Like other forms with adverbial functions, subordinate clauses functioning as adverb clauses are optional, meaning adverb clauses can be introduced and removed without changing the kernel semantics or grammaticality of the main clause (Justice and Ezell 2002: 217; Hopper 1999: 258; Jacobs 1995: 68). For example, adding or deleting the subordinate clause functioning as an adverb clause because she is evil to or from the main clause The kitty stole my milk changes neither the meaning nor the grammaticality of the sentence propositioning that a feline animal usurped my dairy beverage. As an adverb clause, the subordinate clause because she is evil expresses the reason for the occurrence of the main clause and therefore modifies. Conversely, the noun clause That the kitty stole my milk functioning as the subject of the sentence That the kitty stole my milk upsets me cannot be removed without destroying the grammaticality of the sentence as in *Upsets me or changed without altering the meaning of the sentence as in The evil kitty upsets me and That my husband stole my milk upsets me. The noun clause That the kitty stole my milk functions as the subject as opposed to modifying. Therefore, by modifying the entire main clause, subordinate clauses functioning as adverb clauses form close grammatical relationships not with any one word or phrase in the main clause but with the main clause itself (Hopper 1999: 258; Jacobs 1995: 69). Subordinate clauses can therefore occupy any number of positions adjacent to phrases within the sentence. For example, the subordinate clause functioning as an adverb clause when we met him can occupy the positions preceding and following the noun phrase functioning as the subject as well as the position preceding the verb phrase functioning as the predicate in the sentence The puppy licked our faces. Therefore, all three of When we met him, the puppy licked our faces, The puppy, when we met him, licked our faces, and The puppy licked out faces when we met him are grammatically possible in the English language because of the omissibility and flexibility of forms in adverbial functions.
DeCarrico, Jeanette S. 2000. The Structure of English: Studies in form and function for language teaching. Ann Arbor: University of Michigan Press.
Hopper, Paul J. 1999. A short course in grammar. New York: W.W. Norton & Company.
Jacobs, Roderick A. 1995. English syntax: A grammar for English language professionals. New York: Oxford University Press.
Justice, Laura M. and Helen K. Ezell. 2002. The syntax handbook: Everything you learned about syntax…but forgot. Eau Claire, Wisconsin: Thinking Publications.
O’Dwyer, Bernard. 2000. Modern English structures: Form, function, and position. Peterborough, Ontario: Broadview Press.
Quirk, Randolph, Sidney Greenbaum, Geoffrey Leech, and Jan Svarkvik. 1985. A comprehensive grammar of the English language. London: Longman.