Declawing

Declawing is a major surgery known as onychectomy, performed under anesthesia, which removes the tip of each digit (from the first knuckle out) of the cat's forepaws (and rarely the hind paws). The primary reason for declawing cats is to prevent them from damaging furniture; in the United States, some landlords may require that tenants' cats be declawed. Rarely, vicious cats, cats that frequently fight with other pets, or cats that are too efficient at predation of songbirds etc. are declawed. This controversial procedure is uncommon outside of North America, and is prohibited by animal cruelty laws in many countries worldwide.

An alternative to declawing is the application of blunt, vinyl nail caps that are affixed to the claws with nontoxic glue, requiring periodic replacement when the cat sheds its claw sheaths (about every four to six weeks). However, the cat will still experience difficulties because the capped nails are not as effective as claws.

Source : http://en.wikipedia.org/wiki/Cat#Importance_to_Humans