The DK in DK Weight stands for "Double Knitting", and is sometimes known as Light Worsted. You may want to use DK weight for any pattern calling for a 4.5-5.5 mm crochet hook or 3.75-4.5 mm (US 5-7) knitting needles, or a gauge asking for 11-14 stitches per 10 cm. This yarn weight is a happy medium as it knits up more quickly than fingering weight, but is drapier than worsted and Aran yarns