I don't wear breeks, but I do know my dragons.

A Wyvern (a symbol of the old Wessex kingdom - Alfred the great and all that) is a two legged, two winged beastie. A dragon can be four legged or four legged and two winged. A wyrm (as in the Laidley worm or that one from that naughty film with Amanda Donahue in it.....) has no useable limbs (i.e., vestigal limbs like some types of snake, skinks, that sort of thing).

Wales has a dragon. It has six limbs. Four legs, two wings. Don't you ever let me catch you calling it a wyvern again!!!

LTS - whose house is shared with, at the last count, at least 400 dragons in different guises..... including knickers, not breeks.