Marx defined the proletariat as the social class having no significant ownership of the means of production (factories, machines, land, mines, buildings, vehicles) and whose only means of subsistence is to sell their labor power for a wage or salary.
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Capitalist society is made up of two classes—the bourgeoisie, or business owners, who control the means of production, and the proletariat, or workers, whose labor transforms raw commodities into valuable economic goods.