Independent clauses are those combinations of subjects and finite verbs that can stand alone as sentences. Often, however, the logic and rhythm of the paragraph you’re writing makes it desirable to express a closer linkage between two or more independent clauses. There are a number of ways to link them and some errors to avoid.
Fused (Run-on) Sentences
When we join two or more independent clauses in the same sentence, to make what’s called a compound sentence, we need to indicate where one clause ends and the next begins. Otherwise, we’d get what’s called a fused or run-on sentence. Here are three examples of run-ons:
ERROR: Every morning the princess wakes up and kisses the frog this gives her the energy to get on with her day.
ERROR: Fang terrorizes mailpersons he hisses at buses but during pit meetings he refrains from acting venomously.
ERROR: Uncle Charlie is a charter member of the Amalgamated Frogwatchers one of these days he’s going to be president of the group.
If we read these for sentence rhythm, we can easily feel where one clause ends and the next begins. We can mark these boundaries in three ways, depending on how closely we want to relate the clauses. We could make two sentences; we could separate the clauses with a semicolon; or we could join them with a combination of comma plus coordinating connective. There are no rules to tell you when to choose which option; again, it depends on how you are constructing your paragraph.
Coordinating with Semicolons
Semicolons imply that the joined clauses are closely associated.
Every morning the princess wakes up and kisses the frog; she hopes to see it turn into a prince.
Uncle Charlie is a charter member of the Amalgamated Frogwatchers; he’s never missed a spawning.
Joining with Commas and Coordinating Connectives
We can connect independent clauses with a combination of a comma followed by a coordinating connective (and, or, but)—the combination gives a less formal feel to the sentence than a semicolon does, and the coordinating connective states the relationship between the clauses:
Every morning I wake up and coil the cobra, and only then do I oil the elephants.
Fang terrorizes mailpersons and hisses at buses, but he never fails to smile at Ms. Beebs.
Wear your raincoat and galoshes, or the weather wizard will turn you into a giant popsicle.
It’s considered a major error—called a comma splice—to connect independent clauses with only a comma:
ERROR: Every morning I wake up and put bananas in my ears, as a result I don’t have to listen to Jumbo’s stomach rumblings. [After ears, we need at least a semicolon if not a period plus capital letter.]
ERROR: Fang eats animal crackers in bed, he licks the sheets afterwards. [We need at least a coordinating connective just before he.]
Fang eats animal crackers in bed, but he licks the sheets afterwards.
Fang eats animal crackers in bed; he licks the sheets afterwards.
But when two or more independent clauses are quite short and have the same structure, they can be connected by either just a comma or just a coordinating connective:
He’s small but he’s mean.
Fang whines, Miss Hiss giggles.
Beginning Sentences with And, Or or But
Apparently, millions of people think that it’s an error to begin a sentence with a coordinating connective, especially with and. In fact, it’s not an error, but it’s best to have a reason for it: to emphasize a contrast, for instance, or to sum up emphatically:
In the rummage sale I picked up six clowns, five bareback riders, four tigers, three cobras, two fleas, and a whale left over from the aquarium. And I got them all for $17.95 plus tax.
I like coffee, tea, and smooching. But thinking gives me heartburn.
You can kiss the princess and win the kingdom. Or you can go back to the library and study for exams.
Independent clauses can also be linked by commas plus certain other words called marginal connectives. There are five of these:
for (meaning “because”)
nor (“or” with a built-in “not”)
so (meaning “therefore”)
then (“next in time”)
yet (meaning “however”)
Marginal connectives might best be thought of as halfway between coordinating connectives and subordinating connectives, but they’re punctuated like coordinating connectives: the independent clauses they connect are commonly separated by commas:
You can be sure of a messy kitchen, for Fang is cooking tonight.
It isn’t an elephant, nor is it a giant squid.
Monty didn’t like the waiter’s attitude, so he ingested him.
First you put all your fleas on the dog, then you add catsup.
We hate his talking, yet we adore his undulating.
We can also separate the clauses into two sentences, but as is the case when the second clause begins with a coordinating connective, we’d want the extra emphasis (and the informal tone) that results:
He isn’t an elephant,.nor is he a giant squid. Yet he does writhe a lot.
The princess thought that frog was impertinent. So she refused to kiss it.