Which term is used to describe someone who is a member of a royal family, such as a prince or princess?

The term used to describe someone who is a member of a royal family, such as a prince or princess, is "noble." Nobility refers to individuals who hold a high social rank, typically associated with a royal lineage and often possessing titles or estates. Members of the nobility usually have a recognized status in society that is distinct from common citizens, which is why "noble" is the appropriate choice in this context.

The other terms do not accurately describe members of a royal family. A commoner refers to someone who does not belong to the nobility or a royal family and typically has no special privileges associated with their status. A citizen denotes an individual who has legal recognition as a member of a state or nation, which can include both nobles and commoners. An artist is someone engaged in a creative endeavor, and while an artist can belong to any social class, the term does not relate specifically to royal or noble status. Thus, "noble" is the term that specifically indicates membership in a royal family.