Anatomically, a<unk>  is a protuberance in vertebrates that houses the nostrils, or nares, which admit and expel air for respiration in conjunction with the mouth.
In most humans, it also houses the<unk> hairs, which catch airborne particles and prevent them from reaching the lungs.  Within and behind the<unk>  is the olfactory mucosa and the sinuses.  Behind the nasal cavity, air next passes through the pharynx, shared with the digestive system, and then into the rest of the respiratory system. In humans, the<unk>  is located centrally on the face;on most other mammals, it is on the upper tip of the snout.
As an interface between the body and the external world, the<unk>  and associated structures frequently perform additional functions concerned with conditioning entering air (for instance, by warming and/or humidifying it, also for flicking if moving and by mostly reclaiming moisture from the air before it is exhaled (as occurs most efficiently in camels).
In most mammals, the<unk>  is the primary organ for smelling. As the animal sniffs, the air flows through the<unk>  and over structures called turbinates in the nasal cavity. The turbulence caused by this disruption slows the air and directs it toward the olfactory epithelium. At the surface of the olfactory epithelium, odor molecules carried by the air contact olfactory receptor neurons which transduce the features of the molecule into non painful electrical impulses in the brain.
In cetaceans, the<unk>  has been reduced to the nostrils, which have migrated to the top of the head, producing a more streamlined body shape and the ability to breathe while mostly submerged. Conversely, the elephant's<unk>  has become elaborated into a long, muscular, manipulative organ called the trunk.
Nose
Nail 
Atom
Odor
Audios
Pennyroyal
Olea
Eyelid