Q 86. When people are talking about builds here and say either SAD or MAD, what does that mean??
Q 87. What is a capstone?
A86 Single Ability Dependent and Multiple Ability Dependent, respectively. It refers to how many ability scores a character relies on to be effective. A wizard, for example, requires Intelligence for his class abilities, and secondarily on Dex or Con for survivability. He could do well to have any of these three, but is only really dependent on his intelligence. Thus a wizard is fairly SAD. A paladin on the other hand, is meant to tank, making Con important, while his class abilities demand both wisdom and charisma. He'll probably need strength to a debatable extent as well. Thus he relies on Multiple Ability scores, he is a MAD class.
A87 The ability of a class (base or prestige) that you gain at the final level of the class. This determines how useful it is to slog through multiple levels of that class to gain this ability. Some, like the metamind's font of power, are considered strong enough that it can justify losing 5 levels of manifester progression, others are simply subpar. Like the sorceror's, making it more or less a mindless decision to take some other casting PrC.