Scansion
(Credit: London Still)
This is written notation used to explain how a poem (or other text) should be read out loud. It’s kind of like a pronunciation guide, but for a block of text – how to “pronounce” an entire paragraph, for example.
Clearly, this only matters when the text is meant to sound a particular way. A paragraph explaining biology would never have scansion, because that’s just about transmitting data.
Poetry, on the other hand, is usually intended to be read a certain way – in a certain “meter” (rhythm) and line length – so it audibly sounds the way the author intended. Beyond poetry, scansion is sometimes used for poetry-like text (Shakespeare is an obvious example).
Why I Looked It Up
It came up in a NY Times Strands puzzle, where the category was “Poetry.”