Punctuation

1) Commas

Commas separate a dependent clause from an independent clause.

• A dependent clause is an incomplete thought that cannot stand on its own.
• An independent clause is a grammatically complete thought that could form a sentence on its own (independent!).

Here's an example of a proper use of a comma to separate a dependent and independent clause:

Since I had to go to bed early, I decided not go to the movie.

Commas cannot separate two independent clauses because this construction creates a type of run-on sentence called a comma splice.

Incorrect:

I went to the store, I picked up Chris at school.

This is a comma splice. Both of these ideas could be full sentences.

To a fix a comma splice, we can include a conjunction ("and," "but," "however," etc.) or replace the comma with a semi-colon or a period.

Correct:

I went to the store, and I picked up Chris at school.

Correct:

I went to the store; I picked up Chris at school.

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2) Appositives

An appositive is a description of something that came right before it in the sentence. Appositives are always enclosed in two commas, one at the beginning of the appositive and one at the end.

ie. The mayor, who had previously served on the city council, declared that the new ordinance was unwise.

In this sentence, the appositive is "who had previously served on the city council".

To test whether an appositive works, remove the information between the commas. If the sentence still means that same thing and is grammatically correct without the appositive, the appositive has probably been used correctly.

For example:

"The mayor declared that the new ordinance was unwise."

Since this sentence holds up even without the appositive, the original sentence is probably well-constructed.

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3) Quick Comma Rules (that are almost always right):

1. Commas should not come immediately before or after the main verb of the sentence.
2. Commas should not be placed immediately before or after a preposition ("on," "of," "from," "for," "through," etc.).

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4) Semi-colons

Treat semi-colons like periods.

Semi-colons separate two independent clauses. In other words, the clauses before a semi-colon and after a semi-colon can each form a complete sentence individually.

Correct:

I went to the store; later, I picked up Chris at school.

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5) Colons

Colons introduce a list, an example, or a direct explanation.

Correct:

Only three things scare me: public speaking, failure, and mice.

Correct:

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