“Margin” is a very important concept in economics. The living Webster Encyclopedic dictionary of the English Language defines the word “margin” as “a border or edge; a limit, or a condition beyond wich something ceases to exist or be possible”. The margin, in economics,means the boundary or borderline separating the purchases that are worth while from those that are not. It is at the margin that we make a choice among alternatives. Our consumption of any commodity is determined by the decision we make at the margin. Suppose you already have five books on economics and you are contemplating the purchase of a sixth. The contemplated sixth book is known as your marginal volume. Your decision to purchase the book will depend on the additional gain you feel you will get from it and also on the other alternative choices that are open to you to spend your money. In other words, you are considering the marginal worth of the sixth book to you. When you have arrived at this stage,we say that you are on the “margin of consumption”.