Adjective
containing two carboxyls per molecule
Source: WordNetSimilarly for PA 510 PA 611; PA 1012, etc. Other nylons include copolymerized dicarboxylic acid/diamine products that are not based upon the monomers listed above. Source: Internet
Most nylons are made from the reaction of a dicarboxylic acid with a diamine (e.g. PA66) or a lactam or amino acid with itself (e.g. PA6). Source: Internet