Communism in today's world tends to refer to Marxism. All throughout the 20th century, "Communism" tended to refer to Marxism. It is common English usage for people to refer to Marxism with "Communism". It is not incorrect and any pointless semantics debate aside, yes I am referring to Marxism when I say Communism.
com·mu·nism
/ˈkämyəˌnizəm/
Cómo se pronuncia
noun
- a political theory derived from Karl Marx, advocating class war and leading to a society in which all property is publicly owned and each person works and is paid according to their abilities and needs.