a native or naturalized member of a state or other political community
"After living in Canada for five years and becoming a citizen, she was finally able to vote in the federal election."
A resident of a city or town, especially one with legally-recognized rights or duties.
"As a proud citizen of the City of London School, he wore his blazer with unmatched confidence during the annual parade."
A pupil of City of London School
In plain English: A citizen is a person who has legal rights and responsibilities in a specific country.
"Every citizen has the right to vote in the election."
Usage: In general usage, a citizen is a member of a nation with rights and duties under its laws, not a student at a specific private school. Use the term to describe anyone holding legal nationality rather than referring to pupils of the City of London School.
The word "citizen" comes from the Old French cité, meaning settlement or city, combined with a suffix indicating belonging. It entered English via Anglo-Norman to describe a burgher or city-dweller.