Dragons

Dragons are one of the most well known and (in my opinion) coolest of the fantasy creatures. Dragons have been used in many different works, from LOTR to Skyrim, they come in many different shapes and sizes. European dragons normally have two or four legs, a set of wings and scales. While Japanese dragons are more like a flying snake with no wings and small arms.

How they look, how they act, depends on the writer.
Many consider dragons to be wealth hoarders, while other say that they are wise and willing to help.

How they look is kind of standardized between what I would call the 4 groups (classes... Styles) of dragon. 

Normally what I think of when someone says dragon, large/huge lizard, protective scales, sharp fangs and claws, 4 legs, two wings, spews fire, neither good nor evil. Their intellect is left up to the writer, varying from animalistic to mortal (human) intellect.

They sometimes serve the will of the gods/divine beings of a world, or one is a divine dragon itself.

My second favorite way that dragons can look. Wyverns are much akin to the normal dragon, but instead of 4 legs, they only have 2 legs and the wings are set a bit lower, nearly replacing the front two legs. Wyverns sometimes have longer necks, much like the dragons that the Nazgul ride in Lord of the Rings. Though again, this is based on the writer.

The other version of this would would be that the Wyvern has two arms and a large tail to slither on instead of legs.

Personally, anytime someone says a dragon with two limbs instead of 4, I consider it to be a Wyvern.

Worm, Wirm, I have heard it pronounced these two ways the most. I would classify the Japanese dragons in this category.
As the dragon looks more like a snake, or a worm burrowing through the sky. These do not have traditional limbs like the dragon or Wyvern, instead they have smaller arms segmented on the body of the Wyrm. These dragons do not have wings and in Japanese folklore, are considered to be wise, kind and caring towards humanity.

On a side note, it is also somewhat popular for this to be an insult towards dragons and Wyverns. (Sorry Wyrms)

There are two ways to use this, the baby of a dragon, which is used in some of my work. 

The other is a dragon that is half human and half Dragon, like the Drakes in Tales of the Half-Blood, Worlds of the Fey and more. 

Drakes (Human Dragon Hybrid) normally have a mostly human looking body, with patches of scales scattered across the body. They have wings, but I personally don't think they can fly as long as normal Dragons, shaper than normal fingernails, spew fire, and stronger overall.
Drakes normally don't like cold weather due to them being part reptile.

Some use the word Drakeling to refer to a baby dragon, instead of Drake, and I have done so in some of my work as well. Though, as a personal note, I should from now on use Drakeling, when talking about a baby dragon.