When a professor asks you to elaborate on a certain topic based on your own ideas through an essay, it is better to state the original meaning of the idea first before you incorporate your own. If this is the approach you are going to take, then you can employ the definition format of expository essay writing.

A definition basically tells what something means or what it does. In writing definitions, however, you must remember that it has two parts or attributes: the genus and the differentia. The genus states what the idea generally is by discussing its common characteristics. The differentia, on the other hand, states what distinguishes the thing from another entity.

Provided is a sample paragraph that uses the definition format. Take note of the genus (set in bold) and differentia (underlined) used:

• The agenda-setting theory is a theory created by Rogers, Dearing and Bergman which states that the mass media has the ability to influence public opinion by choosing what agenda or issue the public should be talking about. To be able to do this, the mass media acts as gates by choosing what news or issue should be highlighted as important—giving the issue more airtime and more coverage—and what issue should be given less attention.

In writing an expository essay using the definition format, the main definition of the idea appears in the first sentence. The other sentences elaborate the main definition by providing additional details to make it more complete. After this is done, you can now incorporate your own ideas into your essay so your readers can smoothly follow through your train of thoughts.