The objective is to explain that, while the comma is the most-used punctuation mark throughout the kingdom, that use is governed by some basic rules which are easy to grasp, and will keep the ubiquitous comma from becoming a mark amok.
This lesson explains commas as a separator. There's a general comma overview, followed by two text sections of basic rules, exemplified, followed by a quick video which summarizes those rules. Please search SEPARATION PUNCTUATION on Sophia to read about other types.
COMMAS ARE THE MOST USED -- AND THE MOST VERSATILE -- OF ALL PUNCTUATION.
THEY ARE ALSO THE MOST FLEXIBLE, SINCE WRITERS OFTEN HAVE A CHOICE WHETHER OR NOT TO INSERT THEM.
A WRITER SHOULD USE COMMAS JUDICIOUSLY:
TOO MANY COMMAS SLOW DOWN READING AND CAN INTERFERE WITH COMPREHENSION;
TOO FEW COMMAS PROMOTE AMBIGUITY.
Source: Adapted from: The Oxford English Grammar, by Sidney Greenbaum, 1st Ed.
Quick Guide to Commas
1. To separate independent clauses when they are joined by any of these seven coordinating conjunctions: and, but, for, or, nor, so, yet. EX: She was going to fly to Chicago, but her flight was canceled.
2. After introductory clauses, phrases, or words that come before the main clause. EX: Although she was still standing, she was in the front row, and had no idea that everyone else had sat.
3. In the middle of a sentence to set off clauses, phrases, and words that are not essential to the meaning of the sentence. Use one comma before to indicate the beginning of the pause and one at the end to indicate the end of the pause. EX: He knew he'd struck a nerve, however unexpected, because the audience remained rapt.
4. Do not use commas to set off essential elements of the sentence, such as clauses beginning with that (relative clauses). EX: He understood that the exhibit was a quarter of his grade.
5. To separate three or more words, phrases, or clauses written in a series. EX: Her eyes shown brown, blue, and green, depending on how the light hit them.
6. To separate two or more coordinate adjectives that describe the same noun. EX: The tiring, troublesome, and traumatic camping weekend finally came to an end. (Adding a comma between the final adjective and the noun itself is general American usage. NOT adding the comma is journalistic usage. Both are correct; just be consistent throughout your text.)
7. Near the end of a sentence to separate contrasted coordinate elements or to indicate a distinct pause or shift. EX: It lasted for almost 250 years: nothing like it had been known before, nor has been repeated since.
8. To set off phrases at the end of the sentence that refer back to the beginning or middle of the sentence. Such phrases are free modifiers that can be placed anywhere in the sentence without causing confusion. EX: The rookies were having a party, an annual occurrence.
9. To set off all geographical names (EX: Bern, Switzerland), items in dates (except the month and day) (January 23, 2011), addresses (except the street number and name) (222 East Second Street, Atlanta, GA), and titles in names, when they occur at the end of the name. (John Q. Public, Esq.)
10. To separate the main discourse from a quotation. (EX: "That said," the parliamentarian concluded, "there will be a forty-hour party at Buckingham starting now.")
11. To separate a person being addressed from the rest of the sentence. (EX: I suppose, Mrs. Garrett, that you have nothing more to say.)
11. Generally speaking, use commas wherever necessary (but not whenever possible) to prevent confusion or misreading.
Source: The Oxford English Grammar, by Sidney Greenbaum, 1st Ed.
An entertaining, musical, and short video regarding the main uses for commas as separation punctuation.