An essay is a piece of writing, usually from an author's personal point of view. Essays are non-fictional but often subjective; while expository, they can also include narrative. Essays can be literary criticism, political manifestos, learned arguments, observations of daily life, recollections, and reflections of the author.
The definition of an essay is vague, overlapping with those of an article and a short story. Almost all modern essays are written in prose, but works in verse have been dubbed essays (e.g. Alexander Pope's An Essay on Criticism and An Essay on Man).
While brevity usually defines an essay, voluminous works like John Locke's An Essay Concerning Human Understanding and Thomas Malthus's An Essay on the Principle of Population provide counterexamples.