All definitions are taken from Webster's Encyclopedic Unabridged Dictionary of the English Language, unless otherwise specified.
Dragon (drag-on)
A fabulous monster variously represented, generally as a huge,
winged reptile with crested head and terrible claws and teeth, and often
spouting fire.
A female Dragon is called a Dragoness.
The constellation "Draco".
Wyvern or Wivern (wi-vern) Heraldry
A two-legged winged dragon having the hinder part of a serpent
with a barbed tail.
Big Red's Place
Here There Be Dragons
Malathar's World (Dragon ClipArt)
GreenLaire, Home of Ly'szeth the Green
Hydra (hi-dra) Classical Mythology
A water or marsh serpent with nine heads, each of which, if
cut off, grew back as two; Hercules killed this serpent by cauterizing the
necks as he cut off the heads.
Naga (nah-gah)Hindu
A water spirit, half human and half serpent, supposed to bring safety and prosperity
Amphisbaena (am-fis-ba-na) Classical Mythology
A serpent having a head at each end of its body and the ability
to move forward or backward.
Snake Mythology
Naga: The Serpent