Answer:
It is easy to confuse nationality and ethnicity, but there is a major difference between them. Nationality (noun) is the relationship between a person and the political state to which he belongs or is affiliated. Ethnicity (noun) is the identification of a person with a particular racial, cultural, or religious group.
Step-by-step explanation:
Nation is an establishment of a land and a group of people, who are usually not all of the same ancestry. All these people are land-locked, so once they migrate, they are not a part of the nation anymore. Ethnic group is a group of people, who are all of the same ancestry.