Yarn weight refers to the thickness of yarn used by knitters, weavers, crocheters and other fiber artists.

Crochet is a process of creating textiles by using a crochet hook to interlock loops of yarn, thread, or strands of other materials. The name is derived from the French term croc, which means 'hook'. Hooks can be made from a variety of materials, such as metal, wood, bamboo, bone or even plastic. The key difference between crochet and knitting, beyond the implements used for their production, is that each stitch in crochet is completed before the next one is begun, while knitting keeps many stitches open at a time. Some variant forms of crochet, such as Tunisian crochet and broomstick lace, do keep multiple crochet stitches open at a time.