Previously, we’ve learned about conjunctions that join one clause to another. Now we can finally define some of the most important terms in grammar regarding clauses and sentences, and the subject is important enough that it merits a bit of repetition.
As we’ve learned before, a clause is a unit of language that contains one subject and one predicate. That definition overlaps with our working definition of a sentence because every sentence contains at least one clause.
We’ve said that are two general kinds of clauses in English:
An independent clause contains one subject and one predicate, and it contains no word that makes the clause dependent on another clause to be complete. That is, it contains no word like a subordinating conjunction or others that we will learn about. An independent clause is grammatically complete by itself, so it can stand by itself as a complete sentence.
A dependent clause contains one subject and one predicate, and it is not grammatically complete by itself. It functions as part of an independent clause. Dependent clauses include the subordinate clause (which we create with a subordinating conjunction), and other kinds of dependent clauses that we’ll learn about soon.
According to these definitions, this is an independent clause: We fixed dinner for our parents last night.
But if we add a subordinating conjunction to it, it becomes a de- pendent clause that needs to be connected to an independent clause:
Before we fixed dinner for our parents last night . . .
A subordinate clause is one kind of dependent clause. A subordinate clause contains one subject and one predicate, and it must be connected to an independent clause by a subordinating conjunction. The clause above (Before we fixed dinner . . .) is a subordinate clause.
Again, notice the difference between dependent clauses and subordinate clauses: A subordinate clause is one kind of dependent clause. (We’ll study two other kinds of dependent clauses in later chapters: the relative clause and the nominal clause.)
Finally, here is a new definition of a sentence, that important unit of language that we’ve talked about all along:
A sentence is a unit of language that contains at least one independent clause. It may also contain one or more dependent clauses.
Like most definitions of a sentence, this one would not satisfy most linguists (a notoriously argumentative bunch), but it will do for our purposes.
CLASSIFYING BY STRUCTURE
With these definitions, we go on to the well-known, four-part classification of sentences, based on their structures:
- Simple sentences
- Compound sentences
- Complex sentences
- Compound-Complex sentences
You’ve probably encountered them before:
Simple Sentence: A simple sentence contains only one in- dependent clause:
I went to the garage.
A simple sentence can contain a compound subject, a compound predicate, or other compound structures. The sentence below contains one compound subject and one compound predicate, so it’s still a simple sentence:
Alphonse and I went to the garage, found his car, and drove it home.
The following sentence contains a compound subject, a com- pound verb, and a compound predicate:
Jim and Louise planned and prepared the meal and cleared up afterward.
It’s still just one clause, so it’s a simple sentence.
Compound Sentence: A compound sentence contains at least two clauses: two or more independent clauses joined by one or more coordinating conjunctions. There are no dependent clauses in a compound sentence:
I went to the garage, and I found my bike.
I found my bike, but the tires were flat.
Complex Sentence: A complex sentence contains at least two clauses: only one independent clause and one or more de- pendent clauses. In the examples in this chapter, the dependent clauses will be joined to the independent clauses by one or more subordinating conjunctions (shown in bold):
I went to the garage because I needed my bike.
Complex sentences can also contain relative clauses or nominal clauses, as we will soon see.
Compound-Complex Sentence: A compound-complex sentence contains at least three clauses. It contains two or more independent clauses joined by one or more coordinating con- junctions, and it also contains one or more dependent clauses. In the example below, the dependent clause is a subordinate clause, joined by a subordinating conjunction:
I went to the garage because I needed my bike, and I found it.
As we’ll soon see, compound-complex sentences can also contain relative clauses or nominal clauses.
Fragments: There’s a fifth kind of sentence that’s not really a sentence at all. It’s a fragment sentence, a structurally incom- plete sentence, and there are many ways to write them. Here’s one way:
I went to the garage and I found my bike. Because I needed it.
The second sentence is a fragment; it’s simply a subordinate clause that is punctuated like a sentence. We use such fragments all the time in conversation:
Why were you looking for your bike? Because I needed it.
Usually no one objects, or even notices. In careful writing, how- ever, we should avoid fragments unless we’re deliberately using them for emphasis. Even then, we should use them with restraint.
What if we combine two fragments? Do two fragments make a whole? The following consists of two subordinate clauses, punctuated like a complete sentence:
When he finally arrives, if the plane is on time.
Combining two (or more) dependent clauses still makes a fragment sentence, because a sentence has to have at least one independent clause. This kind of fragment is never acceptable, unless you’re Gertrude Stein, and you probably aren’t. (If you are, get in touch with us immediately.)
CLASSIFYING BY PURPOSE
There is another way to classify sentences: according to their purposes. Even in these classifications, sentence structure and punctuation are important.
As we’ve seen, declarative sentences make a statement. They usually have the subject + predicate structure we’ve exam- ined (subject first, predicate second), and they usually end with a period:
I am in trouble.
Interrogative sentences ask a question. They may begin with a question word (Who? What? When? Where? Why? How?) or with a verb. They typically end with a question mark:
Why do these things always happen to me?
How can these things keep happening? Do things like this ever happen to you?
As the third example above shows, many questions (those that can be answered by yes or no) can be formed from declarative sentences by altering the placement of a verb. An auxiliary verb (like do) is placed before the subject:
You know what I’m talking about.
Do you know what I’m talking about?
Sometimes, especially in conversation and fictional dialogue, interrogatives are just a word or two that make sense in context (we hope):
Interrogatives can also be statements that end in tag questions: You did forget your textbooks, didn’t you?
I won’t need them, will I?
These two examples above are not run-on sentences or comma splices. They are correct, completely acceptable sentences, and they’re a bit more complicated than they might look.
As you see in the two examples, a tag question is added to the end of a declarative sentence with a comma, and it repeats the auxiliary verb and the subject of the declarative. If the declarative is positive (You did forget your textbooks), the tag question is negative (didn’t you?). If the declarative is negative (I won’t need them), the tag is positive (will I?).
In other words, negative tag questions anticipate positive answers:
You forgot your textbooks, didn’t you? Oh—yes, I did.
And positive tag questions anticipate negative answers: I won’t need them, will I?
No, you won’t.
But we don’t always get the answer we anticipate, do we? (Or, as the great Fats Waller often said: “One never knows, do one?”)
An imperative sentence is a command. It may end with a period or an exclamation mark, and it may be missing the subject:
Get out of here!
In an imperative sentence, the missing subject is often an implied second-person pronoun (you) perhaps with an implied auxiliary verb:
[You must] Get out of here! [You must] Stop that!
Commands can be phrased more politely, but they’re still imperatives:
Please don’t do that.
Exclamatory sentences express strong emotion. They have no distinctive structure or end punctuation, and they’re often incomplete sentences or just a phrase:
Oh, that’s just great
What the heck?
The four classifications that we just examined illustrate how inadequate simple terms and concepts sometimes are in analyzing what language can do. In some cases, because language is capable of explicit and implicit meanings, sentences don’t clearly fit in any single category; they may have implicit meanings quite different from their explicit purpose.
Suppose a teacher in a classroom says to a student, You look puzzled.
In that context, this declarative sentence may contain an implicit interrogative: Do you have a question?
Or suppose the teacher says to a student in the back row, I’m watching you.
That could be an implicit imperative, meaning Stop what you’re doing! Behave yourself!
The teacher might imply the same imperative idea with a ques- tion: Did you have something to say?
POINTS FOR WRITERS
Beginning sentences with conjunctions.
You may have learned in school that writers should not begin a sentence with the subordinating conjunction because, like this:
Because Linda was late for school, she left home hastily.
In fact, that is a perfectly good complex sentence, and good writers do indeed begin sentences with because. But you shouldn’t do this:
WRONG: Because Linda was late for school. She left home hastily.
As we saw earlier, a subordinate clause has to be connected to an independent clause unless you’re deliberately writing a fragment. You can also begin sentences with coordinating conjunctions,
but don’t overdo it. We’ve done it twice in the last page or so:
But you shouldn’t do this.
And, even then, we should use them with restraint.
The initial conjunction connects the idea of the sentence to the preceding sentences—it’s one way to create paragraph coherence. It also contributes to a somewhat less formal tone, which is desirable in some contexts.
A sentence that begins with a coordinating conjunction is not a fragment sentence. It is a stylistic variation that you should use with restraint.
Commas in compound structures.
When a sentence contains a compound phrase of two parts, commas are usually not necessary:
My brother and your sister are planning a party.
When there are three or more parts in the compound structure, we typically use only one conjunction to join them all, and commas separate the parts:
My brother, your sister, and their friends are planning a party.
As you may have noticed in the examples earlier, compound sentences use a comma to mark the end of every independent clause except the last:
Now you’re behaving yourself, but you have to leave anyway.
You’re behaving yourself now, yet you have to leave, and you can’t come back.
When the two clauses are short and simple, we can omit the comma:
I am angry and I am leaving.
When the clauses are long and complex, the commas separating the clauses become more important. They help the reader understand where one clause begins and another ends.
When a subordinate clause begins the sentence, the comma separates the subordinate clause from the independent clause, unless the subordinate clause is brief and the sentence is unam- biguous without the comma:
Because I could not stop for Death, I hid behind a tree. (Emily Dickinson, improved.)
The sentences below challenge our comprehension (at least a little) because they each need a comma to mark the end of a subordinate clause. Read these sentences and decide where the commas should go:
Because you’ve already eaten dinner at our house tonight will be postponed.
After you’ve eaten the dog should be fed right away.
Yes, we deliberately wrote these sentences to be difficult without the comma. But such sentences do occur in our everyday writing. Commas are important in these cases because they clarify the structure of the sentence for the reader. (If you haven’t yet worked it out, both of those last two examples need a comma after eaten.)