Discourse Communities

The term "discourse community" is often used synonymously with "audience" or "reader(s)." But it is more than that. The term "discourse community" brings together the concepts of "discourse," meaning any form of communication that contributes to a particular body of knowledge, and "community," meaning a group of people that have a common interest.  
dis·course  (dskôrs, -krs)
n.
1. Verbal expression in speech or writing.
2. Verbal exchange; conversation.
3. A formal, lengthy discussion of a subject, either written or spoken.
4. Archaic The process or power of reasoning.
v. (d-skôrs, -skrs) dis·coursed, dis·cours·ing, dis·cours·es
v.intr.
1. To speak or write formally and at length. See Synonyms at speak.
2. To engage in conversation or discussion; converse.
v.tr. Archaic 
1. To narrate or discuss.
com·mu·ni·ty  (k-myn-t)
n. pl. com·mu·ni·ties
1.      a. A group of people living in the same locality and    under the same government.
         b. The district or locality in which such a group lives.
2.      a. A group of people having common interests: the scientific community.
         b. A group viewed as forming a distinct segment of society: the gay community; the community of color.
3.      a. Similarity or identity: a community of interests.
         b. Sharing, participation, and fellowship.
A discourse community can be any set of people who have a reason to communicate with each other. Communication and community both come from the Latin for "common." Both words employ the latin prefix "com," meaning "together." 
A discourse community can be the people in your classroom, the people in your town, the members of your family, the players on your softball team, or even the lady with the felt hat and the boy with the runny nose stuck with you for three hours in an elevator. 
Identifying and understanding the discourse community you are speaking/writing to will help you determine what language is appropriate, what assumptions are shared, and which topics are at issue. You don't talk to your mother as you'd talk to the guy who cut you off in traffic. It's not worth telling the guy next to you about the best sushi joint in town if that guy hates fish. You can't talk about the latest episode of "Days of Our Lives" with someone who does not follow that program. 
Discourse communities are dynamic and must be continuously reassessed. 

Definitions from www.freedictionary.com
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