Armor Mechanics?

Hello everybody. I am working on a comprehensive guide for skill points and armor.

I was wondering how armor reduced damage. Does it just reduce x damage from each hit, kind of like the d&d 4e resist x mechanic? If so, how do you calculate x based on the Def: score for the piece of armor? Also, how does this mechanic stack for when you are wearing different combinations of armor?

On the other hand, does it just reduce damage by x percent, kind of like the Defense stat? If so, how does this stack, and how does it stack with the Defense stat in particular? Is it cumulative or multiplicative?

Thank you in advance.

 

By hovering your mouse over the "Armor" icon (found in your info), you can see the stats of your armor.

 

I'll give an example. Say you have 50% damage reduction. Adding a piece of gear with say 50 defense will then give you a total of 75% damage reduction. (Someone else could probably explain how the math works for armor better, I know.)