Flat, round, static, dynamic: these are all words describing character types in literature. But what do they mean? Flat and round characters easily compare and contrast with each other. In the simplest terms, a flat character exhibits one trait while a round character exudes many traits, even some that conflict with each other.
On the other hand, the terms “static” and “dynamic” refer to the character’s development. In short, a static character does not undergo any significant internal change during the story; a dynamic character evolves through conflict. Thus, you could write about a flat dynamic character, a round static character, etc.