PolyAmides (PA) are a large group of resins that include three sub-classes. The primary sub-class is Nylon (an aliphatic polyamide) in varieties such as Nylon 6 (NY6 or PA6), Nylon 6/6 (NY66 or PA66), Nylon 6/10 (NY610 or PA610) and others. A second sub-class is PolyPhthalAmides (PPA) which are semi-aromatic aramides. Fully aromatic amides are a third subclass which can cross over into being Liquid Crystal Polymers. Wikipedia Link