The narrator of Sir Gawain and the Green Knight often tells the reader directly which traits define a particular character, especially in Gawain’s case. Yet the narrator most often does so not by stating this directly, but by saying what other people think about Gawain, for example, "Gawain was reputed as virtuous," or "he was judged perfect in his five senses" (633, 640, emphasis mine). We get confirmation of these judgments as Gawain rides away from Arthur’s Court. Everyone says it’s a pity that Gawain must die, because "to find his equal on earth is not easy, in faith" (676). Similarly, Arthur "was always judged noblest" among the British kings (26, emphasis ours). This isn’t to say that the narrator never gives his own take on the characters. He explains that Arthur can’t sit down at the feast because "he was so lively in his youth, and a little boyish," and often refers to Gawain as brave or noble (86). But these direct characterizations are equally mixed in with characterizations put into the mouths of others.
Gawain’s actions in the tale pretty much serve to confirm what we already know about him from direct characterization. He’s an honorable knight; therefore, he works hard to keep his promise to meet the Green Knight at the Green Chapel. He’s reputed for courtoisie, or courtly behavior, and sure enough, he delights everyone at Sir Bertilak’s castle with his pleasant manner and conversation. But one action of Gawain’s contradicts what we know about him, and what he knows about himself: when he fails to withhold the green girdle from Lord Bertilak, he acts dishonorably. Of course, he feels terribly about it afterwards and wishes he had acted differently which, once again, confirms his nobility.
One character whose actions are very difficult to interpret is Lady Bertilak’s. When we first meet her, she seems like the very portrait of a lady, she’s so beautiful and courteous. Yet when her husband’s away, she behaves strangely, attempting to seduce Gawain and cheat on her husband with him. Since we can’t quite discern the motive for her actions until the end of the story, they add an element of mysteriousness to Lady Bertilak’s character.
In medieval stories, physical appearances usually indicate something about a character, and Sir Gawain and the Green Knight is no exception. The character whose physical appearance is most symbolic of character traits in the poem is the Green Knight / Lord Bertilak. The Green Knight’s very greenness represents his connection to nature, while the holly branch and axe he carry serve a similar purpose. As Lord Bertilak, the character sports a reddish-brown beard and is "stern-faced, standing firmly on powerful legs; / With a face as fierce as fire" (846-847). The powerful physical appearance matches the power of the man himself. As Gawain concludes, he "seemed truly capable, it appeared to Gawain, / Of being master of a castle with outstanding knights" (849 – 850). And if we know anything about medieval physiognomy, the practice of determining a person’s character traits from their physical appearance, we’re likely to reach the same conclusion.