What do we call a character that provides a contrast to another character?

A character that provides a contrast to another character is known as a foil. The purpose of a foil is to highlight specific traits of another character, often the main character, by presenting opposing qualities or characteristics. This contrast allows readers to gain a deeper understanding of the primary character's motivations, personality, and growth throughout the narrative.

For instance, if one character is confident and bold, the foil may be timid and reserved, thereby emphasizing the first character's confidence. This literary device is commonly used to enhance character development and contribute to the story's themes.

In contrast, a protagonist is the central character, typically involved in the main conflict, while an antagonist opposes the protagonist, creating tension in the story. A supporting character plays a role in aiding the main characters but does not inherently provide that contrasting effect. Thus, the foil is distinctly defined by its function of highlighting differences, making it the correct choice in this context.