RELATED TERMS: Extradiegetic; Narratology; Metalepsis
The term intradiegetic refers to being inside the world of the story. According to Macrae, interpreting Genette, in the context of literary fiction, the simplest ontological structure has three levels: the level of the story (the diegesis), at which the characters exist; the level of the narration (the extradiegesis), at which the narrator exists, for example, through third-person narration; and the level of the real, at which the reader and author exist. In contrast to the reality of the world in which the book is authored and read, the diegesis and the extradiegesis are both fictional. In this schema, the intradiegetic refers to the level of the diegesis.
inside the world of the narrative. This and its contrary term extradiegetic are usually used in reference to the narrator and the narratee, but not necessarily exclusively.
If a space itself, or a series of objects and/or inscriptions within it, is identified by the narratee as telling the story then we can say that the narrator is intradiegetic.
In a more complicated formulation, in a museum a curatorial voice is typically intradiegetic to (inside) the diegesis of the museum itself (but not necessarily narrating the story of the museum, though it could be), but extradiegetic to (outside, telling) the diegesis of the collection or exhibition it is ‘talking’ (sometimes really talking) about.
The narratee can be drawn into the story (intradiegetic narratee) through metalepsis, to become a participant in the world of the story, even to be the protagonist, as is often the case in gaming. In narrative environment design this can be a very powerful tool indeed but needs to be used with discretion, as the intense emotional engagement that it can engender has to be handled with care.
Inside the world of the story. It is typically applied to the narrator (if they are in the story (a character)); the narrator can also be extradiegetic: outside the story, an unknown third part narrator, or someone who is a character in a framing narrative and telling this story.
This is a simplification of the typically Byzantine complexity surrounding these terms in narratology.