Paganism (from Latin paganus, meaning "country dweller, rustic") is a term with various definitions. Originally it was used at the end of the Roman Empire to name those who practiced a religion other than the Abrahamic (Christianity, Judaism, or Islam).
More narrow definitions will not include any of the major world religions. Even more narrow definitions restrict paganism to European pre-Christian religions, with the term often not being applied to, for example, Amerindian religions.
While paganism is sometimes thought of as being strictly polytheistic, some forms were animistic, monotheistic, or pantheistic. For example Neoplatonism influenced the monotheistic Abrahamic religions.
Modern Paganism or Neo-Paganism refers to modern reconstructions/revivals of older pagan religions and sometimes also to movements that are only partially influenced by older pagan religions.