What term describes a fictional narrative that is typically detailed but is shorter than a full-length novel?

The term that describes a fictional narrative that is typically detailed but shorter than a full-length novel is "novella." A novella is a concise narrative that explores characters, themes, and plot in greater depth than a short story, yet it is shorter than a traditional novel, usually ranging from about 20,000 to 40,000 words. This length allows the author to build a more complex narrative arc while still maintaining a focused storyline.

In contrast, an essay is a non-fictional piece that argues a point or presents an idea and does not fit the narrative fiction description. A short story, while a fictional narrative, is generally much shorter than a novella and often focuses on a singular theme or moment. A fable is a short story that typically imparts a moral lesson and often features animal characters, which distinguishes it from the broader category of novellas. Therefore, the correct term in this context is indeed "novella."