Marx discussed this, briefly, twice: "It is always the direct relationship of the owners of the conditions of production to the direct producers..." (Capital III, Int'l Pub., 791) And.... "The owners merely of labour-power, owners of capital, and landowners, whose respective sources of income are wages, profit and ground-rent, in other words, wage-labourers, capitalists, and landlords, consitute then three big classes of modern society based upon the capitalist mode of production."(Capital III, 885)

From Lenin "A Great Beginning" , Collected Works, Vol. 29, p 421: "Classes are large groups of people differing from each other by the place they occupy in a historically determined system of social production, by their relation (in most cases fixed and formulated by law) to the means of production, by their role in the social organization of labor, and, consequently, by the dimensions of the share of social wealth of which they dispose and the mode of acquiring it. Classes are groups of people one of which can appropriate the labour of another owing to the different places they occupy in a definite system of social economy."

To which can be added this: "class divisions are based upon three main criteria: a person's position in the occupational structure, a person's position in the authority structures (how many people a person must take orders from versus how many people a person can give orders to), and a person's ownership of property (or, more specifically, the ownership of property that produces profit, such as stock ownership), which we can call the property structure. These three criteria tend to intersect, producing more of less distinct class divisions." (p.12)

"The working class will be used to signify people with little or no property, middle to low positions in occupation (manual labor), and little or no authority. A further distinction will be made with respect to skilled and unskilled manual workers. At times the term lower class will be used to signify those individuals with no property, who are often unemployed and have no authority (that is, the poor). (p.13). These definitions come from Harold R.Kerbo's Social Stratification and Inequality: Class Conflict in Historical and Comparative Perspective, 3rd edition, McGraw Hill: Boston, 1996. (Compiled by Dr Richard Gibson)