[noun] A wrinkle is a furrow, an inward fold in the surface of the epidermis on and around the forehead, neck, face and/or hands. Wrinkles have a depth of more than 1 millimetre, distinguishing them from fine lines, which are between 0.2 and 1 millimetres deep. Wrinkles result from a gradual loss of skin elasticity as well as slowed cellular renewal, most often due to age, but also caused by harsh external factors.

There are two types of wrinkles:

• Those known as “expression” or “dynamic” wrinkles (with other names such as laugh or frown lines, crow’s feet, etc.), which are associated with frequent facial contractions in distinct areas coupled with the skin tissue’s loss of elasticity.
• Those known as “ageing” or “static” wrinkles resulting from sagging skin as well as external ageing factors (excessive sun exposure, urban environments, poor diet, etc.).