A noun "socialism" represents various economic and political theories advocating collective or governmental ownership and administration of the means of production and distribution of goods, characterized by social and economic equality and the absence of private property.

(Marxism-Leninism) The intermediate phase of social development between capitalism and communism in Marxist theory in which the state has control of the means of production.

Any of a group of later political philosophies such democratic socialism and social democracy which do not envisage the need for full state ownership of the means of production nor transition to full communism, and which are typically based on principles of community decision making, social equality and the avoidance of economic and social exclusion, with economic policy giving first preference to community goals over individual ones.

(chiefly Western, often derogatory, colloquial) Any left-wing ideology, government regulations, or policies promoting a welfare state, nationalisation, etc.