Final answer:
The ability of the hair to stretch and return to its original length without breaking is known as hair elasticity, which is vital for maintaining hair integrity under stress.
Step-by-step explanation:
The ability of the hair to stretch and return to its original length without breaking is known as hair elasticity. This quality is similar to the elasticity found in various materials and objects, which allows them to return to their original shape after being deformed by external forces.
Hair elasticity is essential for maintaining the integrity of the hair strand under stress, such as when brushing or styling. Elasticity in the human body is not only limited to hair but is also a vital property of muscle tissue, allowing it to recoil back to its original length after being stretched or contracted.