A spun yarn characterized by comprising at least 15 wt.% short fibers of polytrimethylene terephthalate and satisfying the relationship: modulus at 5% elongation (%) ≥ 0.1X + 70 wherein X represents the content (wt.%) of the short polytrimethylene terephthalate fibers in the spun yarn. It is excellent in suitability for knitting/weaving, stretchability, and recovery from stretch and has shape stability and durability in long-term wear.