Socialism is the belief that industry should be owned in common. Democratic socialism, socialism and capitalism, a socialist party.
The common ownership can mean state, municipal or worker ownership, and which one is meant is most of the difference between the many kinds. Democratic socialism seeks it through elections. The word covers a very wide range and is used loosely as an insult in some countries and as a party label in others. Note socialist; and that the word dates from 1832.
socialism is a political belief.
French socialisme or social plus -ism, attested from 1832. Social comes from Latin socius, a companion, from sequi, to follow.
French
socialisme
English, today
socialism
Attested since 1832; either from French socialisme or from social + -ism.
Etymology from Wiktionary, CC BY-SA