What is the weight or thickness of yarn?

Yarn weight, also known as yarn thickness, is a classification system used to describe the thickness or diameter of yarn. It's important for determining the suitability of yarn for different types of projects, as well as for achieving the desired texture and drape in finished items. Yarn weight is typically indicated on yarn labels using a standardized symbol or number.

Lace: Very fine yarn used for delicate projects like lace shawls. It's often worked with small needles or hooks.
Fingering/Sock: Thin yarn suitable for lightweight garments and socks. It's commonly used with small needles or hooks.
Sport: Slightly thicker than fingering yarn, suitable for lightweight sweaters and baby items. It's often used with medium-sized needles or hooks.
DK (Double Knitting): A versatile yarn weight suitable for a range of projects, including sweaters and accessories. It's used with medium-sized needles or hooks.
Worsted: Medium-weight yarn commonly used for a wide variety of projects, from garments to blankets. It's worked with medium to large needles or hooks.
Aran: A heavier yarn weight ideal for cozy sweaters and afghans. It's worked with larger needles or hooks.
Bulky: Thick yarn used for quick projects like hats and scarves. It's typically worked with large needles or hooks.
Super Bulky: Very thick yarn suitable for warm and chunky items. It's worked with extra-large needles or hooks.
Jumbo: thick yarn often used for statement pieces like oversized blankets. It's worked with the largest needles or hooks.
It's important to note that the recommended needle or hook sizes can vary based on the specific yarn and the desired gauge (tension) of your project. Always check the yarn label for the manufacturer's recommended needle or hook size, as well as the recommended gauge for accurate results in your knitting or crocheting.