Surprisingly enough, there is no actual difference between hair and fur. Though unique to mammals, hair and fur are chemically indistinguishable and are made of keratin, giving them the same chemical make-up as skin, feathers, and nails.

The purpose of hair and fur seems the same, no matter the host. Many animals couldn't live without its insulating qualities, and many humans appreciate a warmer head, thanks to their hair. Oftentimes, hair and fur serves as protection against injury. An excellent example of this is the thick coat of fur around a lion's neck. This mane will make it very difficult for his enemies to wound him, especially as big cats and other carnivores often go for the throat when hunting. In addition to this, hair and fur can further serve to carry a scent that can vary in purpose from species to species. Although much of the hair that grows on human bodies seems unnecessary, most believe that its growth has greatly reduced, along with our reduced need.

The primary difference between hair and fur, it turns out, is word usage. We generally refer to non-human mammals as having fur, while humans are said to have hair, but there are a few exceptions. When an animal has very coarse or sparse fur, as in the case of a pig or elephant, we usually call it hair. Similarly, a cat or other animal without fur is referred to as "hairless" or even "naked".

On the other hand, we sometimes apply the term fur to ourselves. “He has a hairy chest,” could also be “He has a furry chest.” Generally however fur applies to mammals other than ourselves, unless we are making a deliberate attempt to apply animal characteristics to humans.

Most people are also convinced hair and fur are different because fur tends to grow to a set length. The truth is, in every mammal, hair and fur growth are determined by genetic make-up. So a shorthaired cat doesn’t suddenly become a longhaired cat if it doesn’t get a haircut.

Hair or fur length can also be genetically determined within the variety of humans. Not everyone can grow his or her hair long with equal facility. Ask the many women who have tried and failed. Facial hair is also varied. Some men have a lot, and some very little. Some women have a lot, and some very little! Again, genetics tends to be the primary factor.

We also make the distinction between hair and fur when discussing animal pelts. For the most part, we refer to the pelts of animals and fur: fur coat, fur trim, etc. A few exceptions in the hair and fur distinction for mammals occur here also. For example, mohair is harvested from the alpaca and woven into sweaters and the like. Angora is combed from the angora rabbit and also used in soft sweaters. Often these are both considered hair.