Alternate classes are standalone classes whose basic ideas are very close to established base classes, yet whose required alterations would be too expansive for an archetype. An alternate class operates exactly as a base class, save that a character who takes a level in an alternate class can never take a level in its associated class—a samurai cannot also be a cavalier, and vice versa.
Pathfinder Roleplaying Game Ultimate Combat. © 2011, Paizo Publishing, LLC; Authors: Jason Bulmahn, Tim Hitchcock, Colin McComb, Rob McCreary, Jason Nelson, Stephen Radney-MacFarland, Sean K Reynolds, Owen K.C. Stephens, and Russ Taylor.