Which term describes the permanent straightening of hair?

The term that describes the permanent straightening of hair is lanthionization. This process involves altering the chemical structure of the hair to permanently change its texture from curly or wavy to straight. During lanthionization, disulfide bonds in the hair are broken and then reformed with a straight configuration. This transformation is typically achieved through the use of chemical relaxers that contain ingredients like sodium hydroxide or ammonium thioglycolate.

In contrast, keratinization refers to the natural process where hair strands undergo a transformation to become hardened, affecting the hair's outer layer. Neutralization is a process used in hair treatments to restore the pH balance after a chemical service, and curl reduction pertains to techniques that may make hair less curly but not necessarily permanent, as they might only involve temporary styling methods rather than altering the hair's chemical structure. Thus, lanthionization is the most accurate term for the permanent straightening of hair.