How many types of wool are there?

There are many different types of commercial wool available for knitting and crocheting. The types can be pure wool or wool blends. Each type of wool varies by the animal that the wool comes from (sheep, goats, alpaca, etc.), the grade/quality of the wool, how the wool was prepared/spun, and if the wool is blended with another material such as acrylic. Even with non-commercial wool there would be many variants based upon the type of animal that the wool came from, the grade/quality of the wool, how the wool was prepared and spun, the skill of the person preparing the wool. I have purchased home spun wool that varied greatly in thickness thoughout the entire skein making it difficult to use in a pattern where exact sizing is important.