Which term refers to the overall structure or shape of a literary work that often follows an established design?

The term "Literary Form" is appropriate because it encompasses the overall structure or shape of a literary work, including how the content is organized and presented. This can refer to various established designs such as novels, short stories, poems, or plays, each of which has distinct characteristics that define its structure. Literary form helps readers understand the conventions and expectations that come with different types of writing.

In contrast, "Literary Movement" pertains to a group of writers or works that share a common style or philosophy within a specific historical context, focusing more on the thematic and ideological aspects rather than the structural composition. "Main Idea" refers to the central theme or message of a piece, which does not address the framework of the work itself. Lastly, "Literary Nonfiction" describes a genre of writing that presents factual stories or analysis but does not inherently address the structural design of a work. Therefore, "Literary Form" is the most fitting choice in relation to the question asked.