A compound sentence has at least two independent clauses. An independent clause (unlike a dependent clause) can stand alone as a sentence.
For example:
- Some men are born mediocre, some men achieve mediocrity, and some men have mediocrity thrust upon them. (Joseph Heller, 1923-1999) (Jane Wagner)(This example has three independent clauses.)
In a compound sentence, the two clauses are joined using:
- A conjunction with a comma (e.g., ", and").
When a word like and, or, and but (called conjunctions) joins two standalone "sentences," you should put a comma before it.(The real name for a standalone "sentence" within a longer sentence is independent clause.)
Put a Comma before a Conjunction If It Joins Two Independent Clauses
Words like and, or, and but are known as conjunctions. (There are other conjunctions, but these three are by far the most common.)
(NB: Conjunctions are often used in lists, and the ruling about using a comma before a conjunction in a list depends on whether you're following US or UK writing conventions, or whether you're an advocate of the Oxford Comma.)
Conjunctions that are used to merge two standalone "sentences" (or independent clauses as they're really called) into one using a conjunction. This is a very common practice. When a conjunction is used in this way, it is usual to place a comma before it.
Examples:
He is a great swimmer, but he prefers to play golf. "He is a great swimmer." + "He prefers to play golf." (This is two standalone "sentences" (i.e., independent clauses) merged into one with but. Therefore, a comma is required before but.)
- I may consider your plan, or I may disregard it. "I may consider your plan" + "I may disregard it." (This is two independent clauses joined by the conjunction or. Therefore, a comma is required before or.)
- The applicant must be able to tell jokes and sing, and she must be able to dance.
- (NB: The first and is just a conjunction in a list.) "The applicant must be able to tell jokes and sing." + "She must be able to dance." (This is two independent clauses joined by the conjunction and. Therefore, a comma is required before and.)
- The female applicant must be able to tell jokes, sing and dance. (US)
- The female applicant must be able to tell jokes, sing, and dance. (UK)
(The conjunction and is not joining two independent clauses in this example. Therefore, a comma is not required after sing if you're following UK conventions. In the US (or if you're an advocate for the Oxford Comma), then a comma would be expected after sing.)
A semicolon
A sentence can be extended with a semicolon when a slight break is preferable to a new sentence. (You cannot do the same thing with a comma. That's called a run-on error, and it's a common mistake.)
Merge Two Sentences with a Semicolon
On occasion, a writer may decide that the next sentence is so closely connected to the previous one that a slight break is more appropriate than a new sentence. A semicolon can be used for this purpose.
Examples:
No one was seriously hurt in the accident; one man suffered a broken finger.
In matters of style, swim with the current; in matters of principle, stand like a rock. (Thomas Jefferson, 1743-1826)
The meeting has been rescheduled for 4 o'clock; this reflects the director's new agenda.
A colon (This is rare because the words after a colon are not often an independent clause.)
A colon can be used to introduce some more information about something mentioned earlier in the sentence.
For example:
He wanted just one thing: revenge.
He knew what his wish would be: the ability to turn stones into gold.
A colon is not used to introduce a new idea to a sentence.
For example:
He wanted just one thing: he wanted it since he was boy.
New ideas are introduced by a new sentence or, if you want a smooth transition between the sentences, a semicolon.
For example:
He wanted just one thing. He wanted it since he was boy.
He wanted just one thing; he wanted it si