For humans, haircut, hairstyle, or hairdo normally describe cutting or styling head hair. Human beings of many cultures cut their hair, rather than letting it grow naturally.
Hair styles are often used to signal cultural, social, and ethnic identity. Men and women naturally have the same hair but generally hairstyles conform to cultural standards of gender. Hair styles in both men and women also vary with current fashion trends, and are often used to determine social status.
Hair is genetically programmed to be straight, curly or wavy, and it tends to change over time.
For many years, it was believed that the shape of a person’s hair was determined by the individual hair shafts, and that curly hair was curly because the cross-section of the hair shaft was flatter and had more intertwined layers than straight hair, which was round. But scientists have determined that whether your hair is curly or straight is determined by the shape of the follicle itself and the direction in which each strand grows out of its follicle. Curly hair is shaped like an elongated oval and grows at a sharp angle to the scalp.
Curly hair has a different biological structure from straight hair. It tends to be much drier than straight hair because the oils secreted into the hair shaft by the sebaceous glands can more easily travel down the shaft of straight hair. People with very curly hair may find that this hair type can be dry and often frizzy.
Hair, whether it is curly or straight, is affected by the amount of humidity in the air. It serves as a "truth serum" for the hair, forcing water back into the hair fiber and forcing hair shaft to return to its original structure. This may be more noticeable in somebody with curly hair because it tends to get frizzy when the humidity rises.
