The best definition of nationalism is devotion and loyalty to one’s

country/nation

Explanation:

The nationalism is a political and personal view which has its basis set around devotion and loyalty to one's country/nation. There's multiple forms of nationalism, some being perfectly fine, while some are very extreme. The nationalism can simply be devotion and loyalty to the nation, preserving and cherishing the cultural traits of a particular nation, and living in harmony with the people of other ethnic, racial, cultural groups. On the other hand, there's the extreme form of nationalism. This form of nationalism also is based around the devotion and loyalty to a particular nation, but it is also focused on ethnically pure nation, thus everyone from other ethnicity will face persecution, elimination, torture, or prejudice. This type of nationalism also lifts one's nation as superior compared to the others, spreading hatred and intolerance toward the people from the other ethnic groups.