In characterizations, characters can be defined as round or flat. A round character is one who is described either directly (in an obvious way) or indirectly (through hints). This character is "shown" as being completely described; readers know exactly who the character is. Flat characters (or stock character), on the other hand, is not fully defined or characterized by the author. Instead, this character is a "known," given he or she is a stereotypical character who needs no true description. The character offers nothing more than a filler of a standard part.
Judith Ortiz Cofer's "American History" contains a round and flat character. The round character is Skinny Bones, the protagonist and narrative voice of the text. Indirectly, one can infer that she is a thin, almost skeletal figure (based upon her name). She hates school because she is teased about her body, and she does not excel at sports like the other girls in her ninth grade class. This in-depth characterization illustrates Skinny Bones to be a round character.
The story also includes flat characters: Skinny Bones' mother and father. Readers never hear the voice of Skinny Bones' father; they (readers) only come to know him through "speak" of her father's job. This illustrates him as a stock character. He is the man of the house, and he works to provide for the family. Skinny's mother is also a stock character. During her dialogue, readers can see the typical motherly advice given to a child. Therefore, since both are based upon stereotypical characters, both represent flat characters.