The Craft Yarn Council helps to establish and maintain industry standards for knitting and crocheting in the United States. For example, they have worked to establish a numerical system for identifying yarn weight and encouraging manufacturers and pattern publishers to use that standard system. They've updated their web pages recently. In particular, in addition to standard abbreviations you'll also find standard chart symbols, information on how to read patterns, how to take body measurements, and definitions for skill level. This is a good resource that you may want to bookmark.
Follow this link.