In modern terms these divisions are usually seen as prose narrative, poetry, and drama.
However, classifications of genre are largely arbitrary, based on conventions which give writers a basic medium to explore and the reader or audience particular expectations. In Hamlet (ca. 1600), Shakespeare satirizes the dogmatic genre critics of his time with a list of genres that shows their confusion:
...tragedy, comedy, history, pastoral, pastoral-comical, historical-pastoral, tragical-historical, tragical-comical-historical-pastoral. . . .
A distinction is often made between a genre and a mode. A genre
is a form like a novel,
tragedy, comedy, epic, or sonnet. A mode describes the quality of a part of a larger work; thus a comedy can have passages that are tragic in mode, and a tragedy can have scenes that are in a comic mode (modern criticism often substitutes the more impressive-sounding "comedic," though no-one has yet found a passage "tragedic.")