Final answer:
In 'Sir Gawain,' the pentangle is the main symbol discussed, representing the virtues of knighthood, while other symbols like the green girdle and the Green Knight also contribute to the story's themes.
Step-by-step explanation:
The main symbol that the writer focuses on in Sir Gawain is the pentangle, also known as the endless knot. This symbol is prominently featured on Sir Gawain's shield and represents the five virtues of knighthood that Gawain strives to embody: generosity, courtesy, chastity, chivalry, and piety. Representing truth and the interconnectedness of human and divine principles, it stands as a reflection of Gawain's quest for moral perfection within the narrative.
Aside from the pentangle, other symbols such as the green girdle and the character of the Green Knight himself play crucial roles. The green girdle comes to symbolize Gawain's human frailty and his struggle with sin, while the Green Knight represents the challenges and transformative trials of Gawain's journey.