A "ball of yarn" is a common term to describe the wound up mass of thread used for knitting, crocheting or weaving. However, there are several different synonyms which can be used to describe this item. "Skein" is another term for a ball of yarn, which refers to a long, loose length of yarn wound around itself. "Hank" is a similar term, used to describe a large loop of yarn that is folded into a roughly oval shape. "Wad" is a more informal term for a ball of yarn, used to describe a tangled mass of yarn that has become knotted and difficult to use.