View source for What's the difference between a semicolon and a comma?

The comma is a valuable, useful punctuation device because it separates the structural elements of sentences into manageable segments (Purdue OWL).     
According to the Oxford English Dictionary, the word "comma" comes from the Greek komma, which means "something cut off" or "a short clause" (Wikipedia).

The semicolon is used when you link two independent clauses with no connecting words (Purdue OWL). The word ''semi'' means half.
For example: I am going home; I intend to stay there (Purdue OWL).
          
==Rules==

===Semicolons===

*Use a semicolon between items in a series containing internal punctuation
*between closely related independent clauses not joined with a coordinating conjunction
*between independent clauses liked with a transitional expression (Hacker 251,252).

===Commas===

*Use a comma between coordinate adjectives not joined by ''and''
*before a coordinating conjunction joining independent clauses
*after an introductory word group
*between all items in a series 
*to set off nonrestrictive elements
*to set off transitional and parenthetical expressions, absolute phrases, and contrasted elements
*to set off nouns of direct address, the words ''yes'' and ''no'', interrogative tags, and mild interjections
*with expressions such as ''he said'' to set off direct quotations
*with dates, addresses, titles, and numbers
*to pervent confusion (Hacker 235-245).

==Usuage Semicolon==

===Items in a Series===

The semicolon is always used instead of the comma after items in a series when these items are long or complicated (Word Book).

Classic science fiction sagas are ''Star Trek'', with Mr. Spock and his large pointed ears; Battlestar Galactica, with its Cylon Raiders; and ''Star Wars'', with Han Solo, Luke Skywalker, and Darth Vader (Hacker 252).

===Closely Related Independent Clauses===

A semicolon must be used whenever a coordinating conjunction has been omitted between independent clauses. To use merely a comma creates a kind of run-on sentence known as a comma splice (Hacker 251).

In 1800, a traveler needed six weeks to get from New York City to Chicago; in 1860, the trip railroad took two days (Hacker 251).

===Transitional Expressions===

When a transitional expression appears in the middle or at the end of the second independent clause, the semicolon ''goes between the clause'' (Hacker 252).

Most singers gain fame through hard work and dedication; Evita, however, found other means (Hacker 252).

== Usage Commas==

===Coordinate Adjectives===

When two or more adjectives each modify a noun separately, they are coordinate (Hacker 238).

Roberto is a ''warm, gentle, affectionate'' father (Hacker 238).

===Coordinating Conjunction===

When a coordinating conjunction connects two or more independent clauses- word groups that could stand alone as seperate sentences- a comma must precede it (Hacker 235).

Nearly everyone has heard of love at first sight, but I fell in love at first dance (Hacker 236).

===Introductory Word Groups===

The most common introductory word groups are clauses and phrases functioning as adverbs (Hacker 236).

When Keishawnna was ready to play kickball, her sister held the ball and started to cry.

===Items in a Series===

Unless you are writing for a publication that follows another convention, seperate all items in a series- including the last two- with commas (Hacker 237).

Bubbles of air, leaves, ferns, bits of wood, and insects are often found trapped in amber (Hacker 237).

===Nonrestrictive Elements===

Because it contains nonessential or parenthetical information, a nonrestrictive element is set off with commas (Hacker 239).

For camp the children needed sturdy shoes, ''which were expensive'' (Hacker 239).

===Transitional and Parenthetical Expressions, Absolute Phrases,and Constrasted Elements===

Transitional expressions serve as bridges between sentences or parts of sentences (Hacker 242).

Ja'Niyah did not understand her homework; morever, she was unfamiliar with algebra.

Parenthetical expressions that are distinctly parenthetical should be set off with commas (Hacker 242).

Evolution, so far as we know, doesn't work this way (Hacker 243).

Absolute phrases should be set off with commas(Hacker 243).

Our grant having been approved, we were at last able to begin the archaeological dig (Hacker 243).

Sharp constrasts beginning with words such as'' not'' and ''unlike''  are set off with commas (Hacker 243).

===Nouns of Direct Adress, Words'' Yes'' and ''No'', Interrogative Tags, and Mild Interjections===

Forgive us, Mr. Williams, for burning the Apple pie.

Yes,the doctor will probably see you now.

The film was faithful to the book, wasn't it (Hacker 244)?

Well, cases like these are difficult to decide (Hacker 244).

===Direct Quotations===

"Convictions are more dangerous foes of the truth than lies," wrote philosopher Friedrich Nietzsche (Hacker 244).

===Dates, Addresses, Titles, and Numbers===

In dates, the year is set off from the rest of the sentence with a pair of commas (Hacker 244).

On July 19, 2006, our LitWiki is due.

Alexis Williams was born in Macon, Georgia, in 2003.

If a title follows a name, separate it from the rest of the sentence with a pair of commas (Hacker 245).

Sandra Barnes, M.D.,performed the surgery (Hacker 245). 

In numbers more than four digits long, use commas to separate the numbers into groups of three, starting from the right (Hacker 245).

*3,500
*100,000
*500,000

===Confusion===

Sometimes a sentence will not make sence without a comma.

To err is human; to forgive, is divine (Hacker 245).

==Links==

*Commas vs. Semicolons in Compound Sentences [http://OWL.english.purdue.edu/handouts/print/grammar/g_commacomp.html]
*Using Commas [http://OWL.english.purdue.edu/handouts/grammar/g_comma.html] 
*Wiki encyclopedia [http://en.wikipedia.org/wiki/Comma_%28punctuation%29]
*Punctuation [http://www.aolsvc.worldbook.aol.com/wb/Article?id=ar451700] 

==Works Cited==

*Hacker,Diana. ''A Writer's Reference.'' 5th Ed. Boston: Bedford/St. Martin's, 2003
*"Commas vs. Semicolons in Compound Sentences." OWL.1995-2005 Purdue University ''Online Writing Lab''.7/13/06
<http://owl.english.purdue.edu/handouts/print/grammar/g_commacomp.html> 
*"Using Commas". OWL.1994-2005 Purdue University ''Online Writing Lab''.7/13/06.<http://owl.english.purdue.edu/handouts/grammar/g_comma.html>
*Cooley, Marianne. "Punctuation." ''Word Book Online'' Reference Center. 2006. Word Book Inc.12 July, 2006 <http://www.aolsvc.worldbook.aol.com/wb/Article?id=ar451700>
*"Comma(Puctuation)".Wikipedia.15 July,2006.WikiMedia.''Free Online Encyclopedia''.7/13/06.<http://en.wikipedia.org/wiki/Comma_%28punctuation%29>