Punctuating Compound Sentences
Acompound sentence is a sentence with two or more independent clauses.
There are correct ways and incorrect ways to link independent clauses.
Letís look at the correct ways first.
Solving equations is useful, but studying grammar is fun.
(The linking word is "but." A comma precedes the linking word.)
Simple sentences contain one clause, and compound sentences contain at least two.
(The linking word is "and." A comma precedes the linking word.)
These linking words have names. They are calledcoordinating conjunctions. Sadly, nobody cares. Itís just too many syllables to remember.
That being the case, I call themshort linkers. Thankfully, there are only seven of them.
THE SHORT LINKERS ARE:
Note that if you arrange these guys right, the first letters spell "fanboys."
When two independent clauses are joined by a short linker, put a comma in front of that linker.
However, sometimes independent clauses are joined by longer linking words.
Some students can remember the coordinating conjunctions; however, others can only remember their favorite pizza toppings.
(The linking word is "however." Note that a semicolon precedes it and a comma follows it.)
Grading tests is depressing; consequently, some teachers drink heavily before doing it.
(Again, note the semicolon before the linking word and the comma after it.)
These long linking words are calledconjunctive adverbs. Once again, most folks canít remember that and donít care to. That being the case, I call them "long linkers."
Some common long linkers are:
I can recite lists of coordinating conjunctions and conjunctive adverbs any time of the day or night; therefore, I am idolized by my students.
(Again, note the semicolon before the long linker and the comma after.)
When two independent clauses are joined by a long linker, put a semicolon in front of that linker and a comma behind it.
There is a third way to punctuate compound sentences.
To study math is a treat; to study grammar is a thrill.
(Note the absence of a linking word and the use of a semicolon.)
I like to read; my wife likes to talk.
(Again, note the use of a semicolon.)
Two independent clauses may be linked only by a semicolon.
When only a semicolon is used to link independent clauses, make sure the clauses are thoroughly parallel in structure and word choice.
October days are often beautiful; November days often arenít.
(Note that these clauses contain the same verbs ("are") and the same subjects ("days"). They also contain the adverb "often." These create symmetry and justify the use of a semicolon.)
Letís shift gears for a moment and consider some common errors.
THE FOLLOWING ARE MISTAKES.
DONíT DO THESE THINGS
Math is a pain grammar is worse.
(Note the absence of a linking word and punctuation.)
The example above is afused sentence. A fused sentence occurs when two independent clauses are smooshed together with no punctuation and no linking word.
Math is a pain, grammar is worse.
(This is a little better. At least we have something between the independent clauses, but itís not enough.)
The example above is acomma splice. A comma splice occurs when two independent clauses are joined together with a comma but no linking word.
Math is a pain and grammar is worse.
(Now we have a linking word but no punctuation.)
The example above is arun-on. A run-on occurs when two independent clauses are joined together with a linking word but no punctuation.
Some folks (mainly those with degrees in grammatical pickiness) are intent upon identifying the above errors precisely.
In truth (please donít tell anybody), I just call them all run-ons and forget about it. Doing so frees up more space in my brain to remember baseball statistics.
A Final Word of Caution:
Remember that everything weíve said above applies only to independent clauses. "Short linkers" and "long linkers" often occur in other contexts.
We learn some lessons in the classroom and others in the dorm.
(Note the absence of a comma before "and." It doesnít link independent clauses, so we donít put a comma in front of it.)
Dorm lessons, however, can be just as useful as classroom lessons.
(We donít have a semicolon before "however" because it isnít linking independent clauses.)
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