The word "essay" came to Russian from French and historically goes back to the Latin word exagium (speedypaper review). The French "essai" can literally be translated with the words experience, trial, attempt, sketch, essay.
An essay is a prose work of small volume and free composition, expressing individual impressions and thoughts on a particular subject or issue and not necessarily claiming to be definitive or exhaustive treatment of the subject.
L.P. Krysin's "Explanatory Dictionary of Foreign Words" defines it as "an essay treating any problems not in a systematic scientific form, but in a free form."
"The Great Encyclopedic Dictionary" gives the following definition of an essay: "it is a genre of philosophical, literary-critical, historical-biographical, publicist prose, combining an emphasized individual position of the author with a relaxed, often paradoxical presentation, oriented to colloquial speech."
"The Concise Literary Encyclopedia" specifies: "An essay is a prose work of small length and free composition, treating a private subject and presenting an attempt to convey individual impressions and considerations connected in one way or another with it."