Knitting yarn is a type of fiber used in the craft of knitting, which involves creating fabric by interlocking loops of yarn with needles. It comes in various materials, including wool, cotton, and acrylic, each offering different textures and properties. The thickness of the yarn, known as the weight, can range from fine to bulky, affecting the final appearance and warmth of the knitted item. Yarn is available in a wide array of colors and patterns, allowing for creative expression in knitting projects. It is typically sold in skeins or balls, making it easy to handle while working on scarves, sweaters, or other handmade items.