When we want to knit or crochet something, we need to know the yarn weight, so we can determine what size needles/hook we should use. We all know that for thin yarn, we usually need to use small size needles/hooks, and for thick material we need to use big needles/hooks. Of course when we have a really thin yarn, we know that we can't use 10mm needles/hook. And vice versa: for thick yarn, we can't use 2mm needles/hook. When we use a pattern for our project, the designer usually tells us what type of yarn we should use, and what is the yarn weight s/he recommends for the project. North-Americans, Brits and Australians use different name for the yarn weight. But the symbols on the labels are the same in every continent/countries. What other information can the yarn weight give us about the yarn: Different weight has different gauge with the recommended needles/hook. When we work with thinner yarn, we need more stitches to get the 10cm (4") swatch. And of course the thicke...