Introducing Complex Sentences

So far on this site I’ve been describing the structures of what are called simple sentences, although this is the first time I’ve used that term. In grammar we distinguish simple sentences and complex sentences. These are technical terms in syntax, and I’ll be explaining them shortly, but I want to begin by emphasizing that in both types the basic structures are exactly the same.


I’ll begin by introducing a new word, clause, for something you’ve already had a good deal of experience with. A clause is a group of words containing a single structural backbone (a single subject-finite verb combination) with or without completers. The following are both clauses:

Fang hissed.

Flea powder isn’t a good substitute for Parmesan cheese.

This definition of clause may sound to you like a definition of sentence, and, in fact, very often a clause and a sentence are exactly the same thing. But both terms are necessary because very often sentences contain two or more clauses.

A clause may contain coordinate subjects and finite verbs and still be a single clause. That is, if all the subjects in a clause are subjects of all the finite verbs, there’s still only a single structural backbone.

Eliza, Lisabeth, Betsy, and Bess / Went to the woods and found a bird’s nest.

Since all four subjects in these lines from a nursery rhyme are the subjects of the same two finite verbs, (went and found), there is only a single structural backbone here—a single clause.

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Simple, Compound and Complex Sentences

A clause that can be a sentence on its own is called an independent clause, and a simple sentence is one composed of a single independent clause. This means that the three examples given so far on this page consist of independent clauses that at the same time are simple sentences.

When sentences contain more than one clause, they are no longer simple but “multiple.” There are two kinds of multiple sentences: compound sentences and complex sentences. The difference between them lies in the kinds of clauses they contain.

Compound sentences consist of two or more independent clauses (in effect, simple sentences) joined side by side (compound, from Latin, means “placed together”). The three sentences below are compound sentences. The independent clauses in the first two examples are linked by a comma plus a coordinating connective; the two clauses in the third example are linked by a semicolon:

I like Ms. Beebs, and Ms. Beebs likes me. [Two independent clauses]

The fleas are doing some extra practicing, and Jumbo’s at the physiotherapist’s, but the snakes have taken the day off. [three independent clauses]

The princess kissed the frog; the frog fainted.

A complex sentence also contains two or more clauses, but the clauses are not coordinate. Instead, in complex sentences, one clause contains the other clause. The “contained” clause is called a dependent clause or subordinate clause: both terms are widely used. The clause that “contains” the dependent, or subordinate, clause is the main clause.

How does a dependent clause relate to its main clause? The answer is that it functions within the main clause as a subject, completer, or modifier. In other words, simple sentences are “simple” in that their subjects, completers, and modifiers consist only of phrases. But in complex sentences, at least one subject, completer, or modifier consists of a dependent clause.

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The Rhythm of Dependent Clauses

It’s easy to tell through sentence rhythm whether a clause is independent or dependent. With independent clauses we have a sense of completed movement. The voice takes off at the beginning of the clause and lands at the end. With dependent clauses, however, we sense the movement to be incomplete. Dependent clauses are felt to “hang” or “hover,” as though one end of the clause or the other were suspended in the air.

To test the fact that you can easily feel the difference between independent and dependent clauses, you might try the following exercise. Some of the examples below consist of independent clauses and some of dependent clauses, though I’ve printed all of them without the clues of capital letters or periods. Read each one aloud. If the example feels as though it makes a completed movement—if you can feel your voice taking off and landing—you’ll know it’s independent. If the example feels as though it couldn’t be a sentence by itself, because your voice has to remain hanging, you’ll know it’s dependent. The answers follow the examples:

sharks and piranhas seldom display a sense of humor

you can’t expect color photos from a $2.00 dating service

the horse he slipped and fell on the flea

his particular Olympic sport seems to be whining

because cobras can be touchy

if your elephant isn’t housebroken

when Pandora opened the box

whose toes you tickled

what you said about vultures

The first four examples are single independent clauses. Again, because of the way I’ve punctuated them, they don’t quite look like sentences, but they do sound complete to the ear. The rest of the examples are dependent clauses. They have that hovering feeling because they are sentence components waiting for the rest of their sentences to come along.

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The Two Kinds of Dependent Clauses

There are two kinds of dependent clauses, named after the kinds of words they begin with: subordinating-connective clauses and WH-word clauses. I’ll be discussing these in depth in later, but I’ll briefly introduce them here:

Subordinating-Connective Clauses

because he might be sleeping

if your elephant isn’t housebroken

when Pandora opened that darn box

If you ignore the first words of these clauses and read the rest, you’ll see that what remains in each case is an independent clause capable of being a sentence on its own. It’s the words that introduce the clauses—because, if, and when—that make them dependent. Such words are called subordinating connectives, one of the two kinds of non-coordinating connectives. (The other kind of non-coordinating connective consists of prepositions.)

WH- Word Clauses

whose toes you tickled

what you said about vultures

who neglect their elephants

that she had forgotten to migrate

Clauses like these are called WH-word clauses because their first words begin mostly with the letters wh- (that, in the fourth example, is one of the WH-words). We’re used to WH- words introducing questions, as in the following three examples:

Whose toes did you tickle?

What did you say about vultures?

Who ate all the cobra chow?

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The Functioning of Dependent Clauses

From now on, I’ll be enclosing dependent clauses in curly brackets, like these: {…}. If the dependent clause functions as a subject or completer, I’ll mark it blue for subjects or green for completers. If the clause is a modifier, I’ll indicate the word or phrase that the clause modifies: Here are some examples:

You shouldn’t step on a cobra {because it might be sleeping}. [The “because” clause modifies shouldn’t step, the finite verb of the main clause.]

{If your elephant isn’t housebroken}, you must buy more kitty litter. [The “if” clause modifies must buy, the finite verb of the main clause.]

My computer constantly crashes {since Pandora opened her box}. [The “since” clause modifies crashes, the finite verb of the main clause.]

The elephant {whose toes you tickled} will never forget you. [The “whose” clause modifies elephant.]

Ms. Mallard suddenly realized {that she had forgotten to migrate}. [The “that” clause is the completer of realized.]

{What you said about vultures} brought tears to my eyes. [The ‘what” clause is the subject of brought.]

A person {who has no faults} gives me heartburn. [The “who” clause modifies person, the subject of the main clause.]

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Clauses and Sentences

I’ve had to introduce here what may seem like an avalanche of new terms. All of these, however, follow from the basic concepts of clause structure explored earlier, even though the word clause hadn’t been introduced yet. The only really new concept that we have to deal with is that certain types of clauses function within other clauses. Here is a review of the terms that I’ll be reintroducing on the following two pages:

1. A clause is an arrangement of words that contains a single structural backbone—one subject-finite verb combination. A structural backbone can have coordinate subjects or finite verbs as long as all the subjects are subjects of all the finite verbs.

2. There are two kinds of clauses: independent clauses and dependent clauses (also called subordinate clauses).

a) An independent clause does not have a syntactic function within another clause. Instead, it either stands on its own as a separate sentence or is coordinated, as an equal element, with one or more other independent clauses.

b) A dependent clause functions within another clause, as a subject, completer, or modifier.

c) The two types of dependent clauses are subordinating-connective clauses and WH-word clauses

d) An independent clause that contains a dependent clause is called a main clause.

3. Sentences are classified according to their numbers and types of clauses.

a) Simple sentences contain only one clause, and that clause is independent.

b) Compound sentences contain two or more independent clauses, in a coordinate relationship.

c) Complex sentences contain one or more dependent clauses, which are contained within a main clause. Dependent clauses, again, function as subjects, completers, or modifiers.

–> Continue on to Subordinating Connective Clauses.

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