Traditionally refers to the collection of shaped metal objects which can, when inserted into an appropriate lock and manipulated in n dimensions (because sometimes the locks have to be jiggled with the key, that's why), disengage the locking mechanism.

As Gary Larson has postulated, there are gnomes who steal or move your keys whenever you leave them in an unguarded location. The best defense against these duplicitious fiends is to wear your keys clipped to your belt, beltloop, or nose*.

I advocate the use of non-load-bearing carabiners from any trendy sporting goods store. They come in attractive colors and patterns, feature a range of shapes and closures, and are inexpensive enough to allow for several fashion arrangements.

* Note: Individuals wishing to attempt nasal installation of keys should first consult an accredited plastic surgeon.