Commas, semicolons and colons
Using Commas
There are 5 basic rules for using commas:
1) Commas are used to separate 2 independent clauses that are joined by a conjunction.
An independent clause is a group of words that could, grammatically, exist as its own sentence. Conjunctions are words like: for, and, or, so, but, nor, yet.
The building is finished, but it has no tenants.
2) Commas are used to set off most introductory elements.
An introductory element may be a word or phrase, but it can not be its own sentence.
Unfortunately, the only tenant pulled out.
3) Commas are used to set off non-essential elements.
Many non-essential elements are non-defining relative clauses. This means that the rest of the sentence could exist without these words.
The empty building symbolizes a weak local economy, which affects everyone.
The primary cause, the decline of local industry, is not news.
4) Commas are used to separate items in a series or list.
The city needs healthier businesses, new schools, and improved housing.
5) Commas are used to separate adjectives that modify (describe) the same word.
A tall, sleek skyscraper is not needed.
Do NOT use commas in the following situations:
1) After a subject or a verb.
WRONG: Anyone with breathing problems, should not exercise during smog alerts.
2) Between pairs of words or phrases joined by conjunctions.
WRONG: Asthmatics are affected by ozone, and sulfur oxides.
3) After a conjunction
WRONG: Smog is dangerous and, sometimes even fatal.
4) To set off essential elements
WRONG: Even people, who are healthy, should be careful.
5) After a series or list
WRONG: Cars, factories, and even bakeries, contribute to smog.
6) To set off an indirect quotation
Experts say, that the pollutant ozone is especially damaging.
Semicolons
The semicolon is used to separate equal and balanced sentence elements.
1) It separates complementary main clauses that are NOT linked by a conjunction.
The side effects are not minor; some leave the patient quite ill.
The airline campaign had highlighted only half the story; the other half was buried in the copy.
2) It separates independent clauses that are related by some transitional expression.
The campaign should not have stressed the pilots’ insecurity; instead, the campaign should have stressed the improved performance resulting from that insecurity.
Colons
Colons separate unequal sentence elements.
It separates an independent clause from an explanation or summary.
Many successful advertising campaigns have used this message: the anxious seller is harder working and smarter than the competitor.