The difference between essays and other forms of writing
Barring the obvious answer (to get a degree), in answering this question we need first to ask, what distinguishes an essay from any other form of writing? Most people will have strong intuitions that newspaper articles, scientific reports, and short stories, for example, are not forms of essay, but it might be hard to distinguish exactly why these don’t count as essays.
The difference lies in the stance a writer takes in composing an essay and the kind of thing that an essayist tries to do. We find a clue to the distinction in the general definition of the word “essay”: as a verb it means “to try,” and my dictionary of literary terms calls its noun form “a composition having no pretensions to completeness or thoroughness of treatment” and says that the “chief implication of the term is ‘a tentative study.’”
Essays try to provide an understanding of things that are essentially matters of interpretation, where the prospect of the final word on a subject is remote. In contrast, scientific reports try to describe something that happened (an experiment), and they are supposed to be minimally interpretive and nearly indisputable. Newspaper articles are similar in this way, presenting the facts and just the facts (at least in theory).
But something else must distinguish the essay form, since fictional narratives such as short stories also in some ways present a tentative study of things,. These two forms usually differ in content and aim. Narratives tell stories about how events unfold for characters and usually try to make us feel a certain way. Essays are closer to scientific reports in that their purpose is to tell us, most often explicitly, about the way we ought to understand something.
In sum, whereas a scientific report aspires to be indisputable, an essay strives to give a convincing interpretation of something (and interpretation is by definition disputable). Whereas a short story aims to make us feel, an essay intends to make us think.
Finally, a scientist is supposed to be inessential to her experiment and report; anyone should be able to perform the experiments, get the results, and record them in much the same way. A fiction writer relates to her writing in the opposite way; the story is fundamentally changed when told by anyone else. The essayist, again, falls somewhere between these two extremes. An essay’s argument should be convincing no matter who authors it—the logic of the argument should stand independent of the author—but an essay is also always an expression of the essayist’s opinion, which is by definition not objective fact.
In short, the essayist writes to communicate her opinion on a subject in order to convince her audience to take up this opinion. This is what makes an essay.
Academic essays, in particular, are characterised by a certain standard and approach.
essay. 1960. In S. Barnet, M. Berman, & W. Burto (Eds.), A dictionary of literary terms (pp. 39-40). Toronto, ON: Little, Brown.