Defense Combat Value differs for the kind of attack being done against you.
If it’s a physical attack, then DCV = (B + S)/2
If it’s a magic attack, then DCV = (M + S)/2
Of course, just like ACV, after adding in relevant skills & attributes for each battle situation (thus you’ll have an ever-changing DCV with different enemies), you must roll equal or less to your DCV to succesfully defend and thus take no damage.
Example of physical DCV: Body = 8, Mind = 6, Soul = 8. You have 2 levels in Unarmed Defense (thus +1 to defense), so when an enemy does an unarmed attack against you, your physical DCV will be 9.
However, you can have various defenses: 1)Dodge, 2)Block, and 3)Item Defenses, which is explained furthermore in defending.