The comma is one of the most important punctuation marks, and it is also one of the most misused. Most often, a comma means that the reader needs to pause in his reading. How a comma is used can change the meaning of the entire sentence.
Always use a comma when needed to prevent confusion.
For my research partner I chose Amanda and Josh chose Randall. (incorrect)
For my research partner I chose Amanda, and Josh chose Randall. (correct)
Commas should be used to separate words, phrases, and short clauses in a series. And, yes, always use a comma before the 'and' in a series.
Tigger, Casper and Sasha are the names of my cats. (incorrect)
Tigger, Casper, and Sasha are the names of my cats. (correct)
If all the words in a series are connected by 'and' or 'or', then no comma is needed.
She rode her bike and ran her dog and jumped rope every day.
Some words in the English language are always thought of as pairs, like peanut butter and jelly, bacon and eggs, and Romeo and Juliet. When a pair like this occurs in a series, set it off with commas as you would a single item. Any pairs you happen to create in a series need to be set off the same way.
Breakfast consisted of sausage and biscuits, toast and jam, and scrambled eggs.
When two or more coordinate adjectives modify the same noun, use commas to separate them.
How can you tell whether or not the adjectives are coordinate adjectives? If you can substitute and for the comma and it doesn't change the meaning of the sentence, then they are coordinate adjectives. If when you substitute and for the comma the meaning of the sentence is changed, then no comma is needed.
Mary has long, beautiful hair. You can substitute and for the comma and the meaning of the sentence does not change.
The light blue sedan stood out in the parking lot full of red cars. It makes no sense to say the light and blue sedan, so the use of and changes the meaning of the sentence. The adjectives are not coordinate, so no comma is needed.
When writing a date or an address that consists of two or more parts, you need to use a comma after each part, except between the state and zip code. But you never use a comma when just the month and year are written down.
Her mail goes to Snow White, 527 Fairy Tale Drive, Prince, Dreamland 54321.
She was born on July 20, 1966, in Ashland, KY.
She was born in July 1966.
Commas are not used to set off items separated by prepositions.
The church will meet in the auditorium at the high school on Sunday morning at 10 a.m.
Commas should be used to set off non-essential phrases and clauses.
How can you tell if a phrase or clause is non-essential? When a non-essential phrase or clause is removed from a sentence, it will not change the meaning of the sentence. If the clause contains information that is grammatically essential to the sentence, then it is too important to be set off with commas.
Toddlers, who refuse to obey their parents, should be put in time out.
When the clause is removed from the above sentence, it says that all toddlers should be put in time out, so the commas need to be removed.
Toddlers who refuse to obey their parents should be put in time out.
Commas should be used to set off appositive phrases if the meaning of the sentence would not change without them.
What does an appositive phrase do? It explains or identifies what comes before it.
Rebecca, a good friend of mine, lives in South Dakota.
Commas are used to set off parenthetical expressions that interrupt the main thought of the sentence.
What are parenthetical expressions? Some common ones are for example, you know, and by the way.
My grandson, you know, will be seven-years-old next January.
When words such as yes, no, well, oh, and why are used at the beginning of a sentence, commas are used to set them apart.
No, we are not going to attend the concert.
Commas are used to set off a person's name or words that stand for a person when used in direct address.
Please be patient, Emily, your ride is almost here.
Fellow graduates, I am honored to be speaking before you today.
Commas are used after an introductory adverbial clause, an introductory participial phrase, or two or more adjoining introductory prepositional phrases. If the phrase is short, a comma isn't needed.
Thinking she would wake up on time without the aid of an alarm clock, Cindy didn't bother to buy one.
At times he is unbearable to be around.
Commas are to be used before the words and, but, for, or, nor, and yet when they separate two independent clauses.
Danielle was exhausted from her trip, but she still had to study for her test.
Commas are not to be used between parts of a compound predicate.
Tyler was bored and drew pictures on his schoolwork.
Commas are to be used to separate contrasting elements.
Your dirty clothes go in the clothes basket, not on the bathroom floor.