What is referred to as a brief, intentional deviation from the main topic to express a thought or argument?

A brief, intentional deviation from the main topic to express a thought or argument is termed as a digression. This literary technique allows authors to provide additional insights, context, or commentary that may not fit strictly within the main narrative but adds depth to the discussion. Digressions can enrich the text by exploring related themes or ideas, enhancing the reader's understanding or engagement with the overall work.

In contrast, parenthesis refers to a statement inserted into a sentence that can be removed without altering the main point; while it can provide additional information, it does not always represent a deviation from the topic in the same purposeful way that a digression does. Asides are comments made by a character that are not meant to be heard by other characters, typically used in drama to share thoughts with the audience rather than explore a broader argument. Footnotes are annotations at the bottom of a page, providing further information or references related to specific parts of the text, rather than serving as a departure from the main discussion.