Plant fibre. Cotton plants have soft fluffy tufts around their seeds, and these are harvested and spun into thread and yarn.
Uses. Cotton is a good fibre for warm-weather socks because it breathes well and doesn't retain heat like wool does. Cotton is often used as a substitute fibre for people who are sensitive to wool, and it is also popular with vegans because it is entirely plant-based.
Usually blended. Cotton yarn has very little stretch of its own, so for sock knitting it is usually blended with another fibre such as wool, or elastic nylon. This adds the stretch needed for a snug-fitting pair of socks.
