You may write three or four paragraphs on a topic, but that may not necessarily be an essay. Though your composition may not deviate form the topic, and expressed in effective manner, it may lack the qualities necessary to be regarded as an essay So, it is clear that an essay is written following a definite technique and structure. The word "essay" is defined as a literary composition which treats one subject at a time. It should be simple, clear, direct and present the ideas in an orderly manner. It must be able to reveal the personal thoughts of a writer on a given subject. It is not supposed to be too long but it should be relevant to the subject, properly managed and should possess an adequate power of expression.