A conjunction is a part of speech that connects words, phrases or clauses and shows the relationship between them.  Coordinating conjunctions are used to connect words or word groups when the elements are grammatically equal.  There are several coordinating conjunctions – and, for, but, so, or, yet, nor – depending on the sentence intent. In order for your writing to be clear and free of grammatical errors, it is important to know when and when not to use a comma with a coordinating conjunction.

Before we start, there are a few additional definitions required.

Predicate – The part of the sentence that contains the main verb and all the words in the sentence that come after the verb.  The predicate contains additional information that discusses the action or provides other information about the subject – Thomas ran around the house looking for his book.  (Here ran is the verb which serves as the simple predicate. When combined with all the information in italics, it is a complete predicate).

Independent Clause – Otherwise known as a simple sentence, an independent clause contains a subject and a predicate that works together as an independent unit of thought or meaning – Leslie studied all night for her finals.

Below are situations where commas are required when you use a coordinating conjunction.

Use a comma before a coordinating conjunction that is used to connect two independent clauses.

Ex.  The final work, A Faithful Narrative, was published after the revival was already in decline, yet it created an international stir which would impel further contributions.

Ex.  LULAC, for example, initially denied membership to immigrants and Mexican nationals, and López vehemently denounced the bracero work program and the presence of illegal immigrants.

Use a comma with the coordinating conjunction to separate items in a list if the style you are using requires it.  Most documentation styles such as APA, MLA, and Chicago require a comma before the coordinating conjunction that connects the last element of a series or list when that list contains three or more items.  This will be a factor in most formal academic writing, such as book reviews and research papers.

Ex.  It is the story of immigrant struggles emphasizing the rampant poverty, limited opportunities, and racial tensions that are a part of daily life for residents of this area.

Rhetorical Effects

Sometimes the use of a comma and coordinating conjunction is a rhetorical choice. 

 A comma can be used before a coordinating conjunction if you want to add emphasis.

Ex.  Woodward does not include as extensive a discussion of education as the prior authors, but still emphasizes the divisiveness surrounding educational policy.

Do not use a comma when the coordinating conjunction links parts of the sentence predicate.

Ex.  Residents are forced to rely on each other for aid in tough times and on charity for Christmas gifts.

Test your knowledge of this subject by putting commas before coordinating conjunctions when required.

1. This study compares the Sumerian culture of Mesopotamia and the invention of the cuneiform with the Mayan culture of Mesoamerica and the invention of the glyph system.

2. Eisenhower came to the presidency with the same commitment to wage the Cold War yet he had no new plan for dealing with the Vietnamese situation.

3. A multi-layered book, The White Scourge traces cotton farming from its emergence to its evolution into the corporate model while simultaneously introducing the political, economic, social and gender issues that affected farm laborers.

4. Nonetheless, the book has withstood the test of time and is apt to remain influential in future scholarship.
 

Answers:

1 .This study compares the Sumerian culture of Mesopotamia and the invention of the cuneiform with the Mayan culture of Mesoamerica and the invention of the glyph system.  

No comma is needed here because the coordinating conjunctions connect only parts of the predicate.

2. Eisenhower came to the presidency with the same commitment to wage the Cold War, yet he had no new plan for dealing with the Vietnamese situation. 

A comma is needed before the coordinating conjunction in this sample because the coordinate conjunction connects two independent clauses.

3. A multi-layered book, The White Scourge traces cotton farming from its emergence to its evolution into the corporate model while simultaneously introducing the political, economic, social, and gender issues that affected farm laborer.

This sentence is part of a book review, which would need to be written in a formal documentation style.  A comma is needed before the coordinating conjunction because the conjunction connects items in a list of three or more elements.

4. Nonetheless, the book has withstood the test of time, and is apt to remain influential in future scholarship.

Here the comma is optional.  One is used with this particular sentence because the continued influence of the work is being emphasized.  However, it would have been grammatically correct without it.
 

Related Academic Center Resources

This week writers may also be interested in Shawn Brett's discussion of When and How to use a Comma with a Coordinating Conjunction, a previous issue of Grammatically Correct published on 9/14/04, or our handout on Comma Splices and Fused Sentences.
 

Recommended Grammar Website of the Week

This week we recommend the Online Writing Lab site of Purdue University.  This link http://owl.english.purdue.edu/handouts/grammar/g_comma.html is to their page that contains additional information on comma use.