Nylon 6 can be modified using comonomers or stabilizers during polymerization to introduce new chain end or functional groups. It is a semi crystalline polyamide. Unlike most other nylons, nylon 6 is not a condensation polymer, but instead is formed by ring-opening polymerization; this makes it a special case in the comparison between condensation and addition polymers. Its competition with nylon 6,6 and the example it set have also shaped the economics of the synthetic fiber industry.