Depending on the guidelines that your school provides, the formatting of your essay will differ, but there are a few things your paper will always need. If you used other people's work in your definition essay, you will have to cite it properly. Remember to include footnotes, end notes or in-text citations. Also, you will need to have a bibliography or works cited list at the end of your paper. Your teacher or professor may also want you to annotate your works cited list by writing a couple of sentences about each of your sources and how they contributed to your essay. You will likely also have to provide a title page with the title of your essay, your name, date, class and instructor.
The function of an argumentative essay is to show that your assertion (opinion, theory, hypothesis) about some phenomenon or phenomena is correct or more truthful than others'. The art of argumentation is not an easy skill to acquire. Many people might think that if one simply has an opinion, one can argue it successfully, and these folks are always surprised when others don't agree with them because their logic seems so correct. Argumentative writing is the act of forming reasons, making inductions, drawing conclusions, and applying them to the case in discussion; the operation of inferring propositions, not known or admitted as true, from facts or principles known, admitted, or proved to be true. It clearly explains the process of your reasoning from the known or assumed to the unknown. Without doing this you do not have an argument, you have only an assertion, an essay that is just your unsubstantiated opinion.