<unk>  is a filamentous outgrowth of protein, found only on mammals. It projects from the epidermis, though it grows from<unk>  follicles deep in the dermis. Although many other organisms, especially insects, show filamentous outgrowths, these are not considered "hair". So-called "hairs" (trichomes) are also found on plants. The projections on arthropods, such as insects and spiders are actually insect bristles. The<unk>  of non-human mammal species is commonly referred to as fur. There are varieties of cats, dogs, and mice bred to have little or no visible fur. In some species,<unk>  is absent at certain stages of life.
The primary component of<unk>  fiber is keratin. Keratins are proteins, long chains (polymers) of amino acids.
Hair
Tissue 
Wart
Biomedical tissue
Boil
Skin appendage
Wound
Nail 