Hair is a filamentous biomaterial, that grows from follicles found in the dermis. Found exclusively in mammals, hair is one of the defining characteristics of the mammalian class.

The human body, apart from its glabrous skin, is covered in follicles which produce thick terminal and fine vellus hair. Most common interest in hair is focused on hair growth, hair types and hair care, but hair is also an important biomaterial primarily composed of protein, notably keratin.

The word "hair" often refers to two distinct structures:

1. the part beneath the skin, called the hair follicle or when pulled from the skin, called the bulb. This organ is located in the dermis and maintains stem cells which not only re-grow the hair after it falls out, but also are recruited to regrow skin after a wound;
2. the shaft, which is the hard filamentous part that extends above the skin surface. A cross section of the hair shaft may be divided roughly into three zones.

Hair fibers have a structure consisting of several layers. Starting from the outside:

1. the cuticle which consists of several layers of flat, thin cells laid out overlapping one another as roof shingles,
2. the cortex, which contains the keratin bundles in cell structures that remain roughly rod-like; and in some cases,
3. the medulla, a disorganized and open area at the fiber's center.

Hair is a 1979 film based on the 1968 Broadway musical of the same name about a Vietnam war draftee who meets and befriends a tribe of long-haired hippies on his way to the army induction center. The hippies introduce him to their countercultural lifestyle of marijuana, LSD, "be-ins", and protests.

Unsourced

• "Of course I'm crazy! We're all crazy. Let's shake on it."

-Jeanie Ryan

• "The draft is white people sending black people to make war on the yellow people to defend the land they stole from the red people!"

-A Hippie

• Berger: Where you from? Claude: Oklahoma. Jeannie: Hey, listen. I know what it's like. I used to be from Kansas myself.

-When the gang first meets Claude

• Prison Psychiatrist: And men? Woof: What do you mean...? Prison Psychiatrist: You have any sexual attraction towards men? Woof: You mean if I'm a homosexual or something like that? Prison Psychiatrist: Yeah. Woof: Well, I wouldn't kick Mick Jagger out of my bed, but uh, I'm not a homosexual, no. -After Woof refuses to let his hair be cut

• Woof, Hud, Berger: [in song] Oh say, can you see my eyes? If you can, then my hair's too short.

-During song, Hair.