In a writer's toolkit, few things are more versatile than a compound sentence. By definition, these sentences are more complex than a simple sentence because they contain two or more independent clauses. They are what gives an essay detail and depth, making your writing come alive in the reader's mind.
In English grammar, a compound sentence can be thought of as two (or more) simple sentences joined by a conjunction or an appropriate mark of punctuation. It is one of the four basic sentence structures. The others are the simple sentence, the complex sentence, and the compound-complex sentence.
Regardless of how you structure a compound sentence, it signals to the reader that you are discussing two equally important ideas. There are three primary ways of doing so.
A coordinating conjunction indicates a relationship between the two independent clauses, whether contrasting or complementary. It is by far the most common means of joining clauses to create a compound sentence.
Example: Laverne served the main course, and Shirley poured the wine.
Spotting a coordinating conjunction is fairly easy because there are only seven to remember: and, but, for, nor, or, so, and yet.
A semicolon creates an abrupt transition between the clauses, usually for sharp emphasis or contrast.
Example: Laverne served the main course; Shirley poured the wine.
Because semicolons create such an abrupt transition, use them sparingly. But you can write a perfectly good essay and not need a single semicolon.
In more formal written instances, a colon may be employed to show a direct, hierarchical relationship between clauses.
Example: Laverne served the main course: It was time for Shirley to pour the wine.
Using a colon in a compound sentence is rare in everyday English grammar; you're most likely to encounter its use in complex technical writing.
Simple vs. Compound Sentences
In some occasions you may be unsure of whether the sentence you're reading is simple or compound. An easy way to find out is to try dividing the sentence into two simple sentences. If the result makes sense, then you've got a compound sentence.
Simple: I was late for the bus. The driver had already passed my stop.
Compound: I was late for the bus, but the driver had already passed my stop.
If the result does not make sense, however, you have a different kind of sentence. These may be simple sentences, with no subordinate clauses or they may contain subordinate clauses:
Simple: When I left the house, I was running late.
Compound: I left the house; I was running late.
Another way to determine whether a sentence is simple or compound is to look for verb phrases or predicate phrases:
Simple: Running late, I decided to take the bus.
Compound: I was running late but I decided to take the bus.
Lastly, bear in mind that while compound sentences are great for variety's sake, you shouldn't rely on them alone in an essay. Complex sentences, which contain multiple dependent clauses, can express detailed processes, while simple sentences can be used for emphasis or brevity.