There are two types of purposes: a general purpose and a specific purpose.
The general purpose is one of three options:
- to inform: to share information with listeners by defining, describing, or explaining a thing, person, place, concept, process, or function.
- to persuade: to change or reinforce a listener's attitude, belief, value, or behavior.
- to entertain: to help listeners have a good time by getting them to relax, smile, and laugh.
For more information about general purposes and a chance to check what you have learned:
http://www.wisc-online.com/Objects/ViewObject.aspx?ID=SPH2301
The specific purpose requires two steps:
- identify a behavioral objective: what do you want your audience to do after your speech
- formulate the specific purpose: a goal statement that focuses your speech on the audience
More explanation on the topic of specific purposes:
http://www.wisc-online.com/objects/ViewObject.aspx?ID=SPH3001
Three guidelines for preparing your specific purpose:
- use words that refer to observable or measurable behavior
- limit the specific purpose to a single idea
- reflect the needs, interests, expectations, and level of knowledge of your audience
Having a specific purpose will help keep you on track while preparing your speech.