What term refers to the personality or activity by which a person is known?

The term that best describes the personality or activity by which a person is known is "identity." Identity encompasses the various characteristics, qualities, and beliefs that define an individual. It includes how individuals see themselves and how they are recognized by others, forming a comprehensive picture of who they are in various contexts, such as cultural, personal, or social settings.

In contrast, while "reputation" refers to the beliefs or opinions that others hold about a person based on their actions or behavior, it is more focused on external perception rather than internal essence. "Character" often pertains to the moral and ethical qualities of an individual, indicating their distinctive attributes, but it doesn't capture the full scope of identity. Lastly, "persona" indicates a mask or facade that one presents to others, often for specific roles or situations, and may not reflect the true self or complete identity of an individual. Therefore, identity is the most encompassing term regarding the characteristics that define how a person is known.