Everything you always wanted to know about commas and more!

 
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Ever wonder why your English teachers make you learn those crazy parts of speech?  I always made it point to my students exactly why: one reason is so you can apply the comma rules.  Knowing you need to follow an introductory participial phrase with a comma doesn't mean much if you can't recognize the participial phrase in the first place.  If you don't know your parts of speech, these rules won't help much.

1.  Use commas to separate items in a series.  The items can single words or phrases or clauses—anything.

 
2.  Use a comma to separate two adjectives that precede a noun under the following circumstances: if the adjectives can be transposed (turned around) or if the word and can be placed between them without affecting the meaning. Participles without phrases, since they act like adjectives, are also targeted by this rule.
(Use a comma since the adjectives can be transposed--Mr. Roden is an exuberant, wonderful man—and and can be inserted— Mr. Roden is a wonderful and exuberant man)

 
3. Use a comma to separate independent clauses in compound sentences when the clauses are joined by a coordinating conjunction (unless they're very short clauses of two or three words).  When they are joined with for or yet, use a comma regardless of their length.

4.    Use a comma after introductory elements.  Introductory elements precede any independent clause.  Consequently, they are often found at the beginning of sentences, but look for them elsewhere in compound or compound- complex sentences.

                

4a.  Mild exclamations are exclamations not strong enough to require an exclamation mark. These include words like why, no, oh, well, and  yes --unless they're part of the sentence as in the second example.
4b.  Prepositional phrases of four or more words (unless the phrase precedes a verb followed by its subject--second example.)
4c.  Participial and infinitive phrases  (when the infinitive phrase isn’t used as the subject)
4d.  Adverb clauses     

5.  Use a comma to separate the elements in dates and addresses.

6.  Use a comma after the salutation of a friendly, informal letter and after the closing of all letters.
7.  Use commas to set off nouns of direct address.
8.  Use commas to set off parenthetical expressions.  Most transitions are parenthetical as are some subject and verb combinations.

Essential elements limit the possibilities for the noun they rename or describe by telling which one or ones. The rest are nonessential and are set off by commas.  

9.  Use commas to set off nonessential appositives.
10.  Use commas to set off nonessential  subordinate clauses or  participial phrases.  Clauses that are nonessential begin with which while essential ones begin with that.

11.  When dealing with dialogue, use commas to separate the attribution (who said it) from the quote. Note when the comma is inside the quote and when it isn’t.

12.       Use a comma before/after a contrasting expression.  Words like unlike or not signal an upcoming contrasting expression.

13.       Use a comma after single-word modifiers.  These are adjectives or adverbs that are out of their normal position near the word they modify.
14.       To prevent confusion between numbers and names.
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