Which term did Karl Marx use to describe the working class?

Karl Marx used the term "proletariat" to specifically refer to the working class within his theoretical framework of class struggle and capitalism. He defined the proletariat as those individuals who sell their labor for wages and do not own the means of production. Marx's analysis focused on the relationship between the proletariat and the bourgeoisie, the latter being the class that owns the means of production and capital. This distinction is central to Marxist theory, as it highlights the conflicts arising from economic disparities and the exploitation of the working class by those who control resources. The other terms, while related to labor and work, do not capture the specific socio-economic context that Marx attributes to the proletariat.