Final answer:
GATGK uses modern English and verse form, whereas The Canterbury Tales is in Middle English and also in verse but with a longer collection of stories.
Step-by-step explanation:
The language of 'Gawain and the Green Knight' (GATGK) is different from 'The Canterbury Tales' primarily because GATGK uses modern English while The Canterbury Tales is written in Middle English. Furthermore, 'The Canterbury Tales' is presented in a verse form with a rhyming scheme and is structured as a collection of stories told by different pilgrims, while GATGK, although also utilizing a verse format, employs a more contemporary language style. Additionally, it's important to note that both works are considered fictional, even though they may draw from historical contexts or legends, such as the Arthurian legends referenced in GATGK. In terms of length, 'The Canterbury Tales' is indeed much longer, containing multiple tales with a variety of characters and plots.