Tawddgyrch cadwynog is a Welsh syllabic verse form built around linked rhymes or repeated sound patterns, so that one line leads into the next like a chain. It belongs to the tradition of strict Welsh meters and is related to the rhupunt, though the exact pattern can vary in practice and historical usage.
Example
Silver on the hill, the river turns to light,
Light touches the reeds, the reeds bend in the wind,
Wind carries the song into the darkening night.