A Predator's "derivation" is his or her removal from the original source. In other words, his or her removal from The Ancients. It's a simple concept to grasp, really. Any Predator born of one of The Ancients is of the first derivation. Any Predator born of that predator would be second derivation, and so on.

        As easy to grasp as that may be things can get complicated when two Predator's of different derivations produce a child. Say you have a Predator who is fourth derivation and it gets together with a Predator of fifth derivation. Together they produce a child. What is it's derivation? Fourth or Fifth? 4.5? In situations like this, to keep things simple, always consider the Predator actually giving birth to the child to be the prime factor. It is her derivation that the child will inherit, regardless of the father's derivation. This may not exactly be fair in some cases, but it is the easiest way to handle things to keep things from being too complicated.
        Basically, the mother plays a larger role in the child's development than the father. All he did was supply a little Predator sperm to help get the ball rolling, so to speak. It is the mother's body (and blood) that assists the child in it's greater development.

        How are derivations used in conjunction with the age scale terms? To help explain this we will use Raphael, one of my own characters, as an example. Raphael is a Primorian Neophyte. Meaning he was born of Primorian stock and was born in the 20th century. Just because he has the term Neophyte applied to him doesn't automatically mean that his derivation is low (or high, as the numerical case may be). He could boast a derivation of third or fourth and still be considered a Neophyte because of when he was born, not who he was born from.