Yarn is a descriptive term for any spun thread. Yarn for crochet can be natural wool, but so can acrylic, polyester, bamboo or cotton.
The Ultimate Guide to Yarn Weights and Crochet Hook Sizes
Can you Mix Yarn Weights in Crochet?
The BEST Yarn for Crochet Beginners: A COMPLETE Guide - sigoni macaroni
Swish Worsted Weight Yarn Review - The Loopy Lamb
Can I Use a Different Weight Yarn for My Project? - Ambassador Crochet
Solved: Does Crochet Hook Size Matter?
1PCS Yarn for Crocheting,Soft Yarn for Crocheting,Crochet Yarn for Sweater,Hat,Socks,Baby Blankets(Pink NO Hook)
Crochet hook for the yarn weight, secrets on how to choose
How to Match Crochet Hook Size and Yarn Weight
Easy Guide to Combining Yarn Weights for Amigurumi
Yarn For Crochet - Weights, Hooks and Styles
What Size Crochet Hook for Blanket? - love. life. yarn.
Yarn Weights - Standard Weights for Crochet & Knitting
How Do You Match A Crochet Hook To Your Yarn? – Darn Good Yarn