An imaginary creature from old European stories: a dragon-like animal with wings and only two legs, usually with a long tail that ends in a point or an arrow shape. Say it "WY-vern," with the first part sounding like the word "why." The two legs are the whole point of the word. A dragon in most European pictures has four legs plus wings; a wyvern has two back legs and uses its wings like front limbs, rather as a bat does. Because of that difference, people who care about old shields and flags — heraldry, the study of coats of arms — insist the two words are not the same. In ordinary life almost nobody keeps them apart, and most English speakers would just say "dragon" if they saw one. So the word lives mostly in three places: on old coats of arms and family badges, in fantasy books and role-playing games, and among people who enjoy that kind of detail. Notice too that a wyvern is not the same as a wyrm or worm, an old word for a legless serpent-dragon. It is a rare, slightly bookish word — using it correctly signals that you know your monsters.

雙足飛龍（西方紋章與奇幻作品中的兩腳有翼龍）