Nationalism is a term used to describe a unified group of people with a common language or culture who have a goal of building and maintaining their sovereignty through self-governance over its homeland, without a need for a hereditary ruling family such as a monarchy, and by forming an elected body to formulate laws and policies by majority vote or approval.
Nationalism is also, by its nature, an idea that one's own culture and interests are better than anyone else's and manifests itself in patriotic gestures of support from within and displays to influence international opinion, as well as a disapproval of any globalist or internationalist type of coalition, whether it be politically or commercially, which might reduce their sovereignty.
