A claw is a curved, pointed appendage, found at the end of a toe or finger in most mammals, birds, and some reptiles. Somewhat similar fine hooked structures are found in arthropods such as beetles and spiders, at the end of the leg or tarsus for gripping a surface as the creature walks. A claw is made of hard protein called keratin.
Claws are used to catch and hold prey in carnivorous mammals such as cats and dogs, but may also be used for such purposes as digging, climbing trees, etc, in those and other species.
Similar appendages which are flat and do not come to a sharp point are called nails instead.
The correct term for an arthropodâ€™s â€˜clawâ€™ is a chela (plural chelae). Legs bearing a chela are called chelipeds. Chelae are also called pincers.
In tetrapods, claws are made of keratin and consist of two layers. The unguis is the harder external layer, which consists of keratin fibers arranged perpendicular to the direction of growth and in layers at an oblique angle. The subunguis is the softer, flaky underside layer whose grain is parallel to the direction of growth. The claw grows outward from the nail matrix at the base of the unguis and the subunguis grows thicker while travelling across the nail bed. The unguis grows outward faster than the subunguis to produce a curve and the thinner sides of the claw wear away faster than their thicker middle, producing a more or less sharp point. Tetrapods use their claws in many ways, commonly to grasp or kill prey, to dig and to climb and hang.
A talon is the claw of a bird of prey, its primary hunting tool. The talons are very important, without them the bird would not be able to catch its food.