An essay is usually a short piece of writing. It is often written from an author's personal point of view. 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.

It is very difficult to define the genre into which essays fall. Aldous Huxley, a leading essayist, gives guidance on the subject:

Like the novel, the essay is a literary device for saying almost everything about almost anything, usually on a certain topic. By tradition, almost by definition, the essay is a short piece, and it is therefore impossible to give all things full play within the limits of a single essay. But a collection of essays can cover almost as much ground, and cover it almost as thoroughly, as can a long novel. Montaigne's Third Book is the equivalent, very nearly, of a good slice of the Comédie Humaine. Essays belong to a literary species whose extreme variability can be studied most effectively within a three-poled frame of reference. There is the pole of the personal and the autobiographical; there is the pole of the objective, the factual, the concrete-particular; and there is the pole of the abstract-universal. Most essayists are at home and at their best in the neighborhood of only one of the essay's three poles, or at the most only in the neighborhood of two of them. There are the predominantly personal essayists, who write fragments of reflective autobiography and who look at the world through the keyhole of anecdote and description. There are the predominantly objective essayists who do not speak directly of themselves, but turn their attention outward to some literary or scientific or political theme. … And how splendid, how truly oracular are the utterances of the great generalizers! … The most richly satisfying essays are those which make the best not of one, not of two, but of all the three worlds in which it is possible for the essay to exist.

Etymology

The word essay derives from the French infinitive essayer, "to try" or "to attempt". In English essay first meant "a trial" or "an attempt", and this is still an alternative meaning. The Frenchman Michel de Montaigne (1533-1592) was the first author to describe his work as essays; he used the term to characterise these as "attempts" to put his thoughts adequately into writing. Inspired in particular by the works of Plutarch, a translation of whose Oeuvres morales (Moral works) into French had just been published by Jacques Amyot, Montaigne began to compose his essays in 1572; the first edition, entitled Essais, was published in two volumes in 1580. For the rest of his life he continued revising previously published essays and composing new ones.