What is the term for a character who is not well-developed and exhibits few distinct traits?

The term that describes a character who is not well-developed and exhibits few distinct traits is a flat character. Flat characters are typically one-dimensional, lacking depth and complexity; they often represent a single idea or value and do not undergo significant personal growth or change throughout the story. This characterization allows them to serve specific functions in the narrative, such as providing contrast to round characters or advancing the plot without the need for deep emotional engagement.

In literature, flat characters can be useful for driving certain themes or illustrating particular points without the nuances that a more developed character would bring. They may be static figures who remain the same throughout the story, emphasizing the journey or transformation of more complex characters.