Abstract: Polyamide 56 filaments having a relative viscosity in sulfuric acid of 3 to 8, an Mw/Mn ratio of 1.5 to 3, a single fiber fineness of 0.1 to 7 dtex, a strength of 7 to 12 cN/dtex, a shrinkage rate of 5 to 20% after having been subjected to boiling water treatment at 98° C. for 30 minutes, a strength of 5 to 11 cN/dtex after the boiling water treatment and a stress at 10% elongation of 0.3 to 1.5 cN/dtex after the boiling water treatment.

Abstract: A crimped yarn includes a synthetic fiber which contains an aliphatic polyester resin (A) and a thermoplastic polyamide resin (B) and exposed area ratio of the aliphatic polyester resin (A) with respect to fiber surface area is 5% or less and a crimp is imparted to a multifilament comprising said synthetic fiber, and a fiber structure containing said crimped yarn as at least a part thereof. Furthermore, a crimped yarn in which the aliphatic polyester resin (A) and the thermoplastic polyamide resin (B) are constituted of a polymer alloy type synthetic fiber, or a crimped yarn constituted by a sheath/core type composite fiber in which the core component comprises the aliphatic polyester resin (A) or a polymer alloy of the aliphatic polyester resin (A) and the thermoplastic polyamide resin (B) and the sheath component comprises the thermoplastic polyamide resin (B), and a fiber structure containing said crimped yarn as at least a part thereof.