Nose is an organ that projecting above the mouth on the face of higher vertebrates (reptiles, aves and mammals), containing one pair of nostrils and detecting smells. Nose is also used for breathing.
Fishes and amphibians have one or two pairs of nostrils (one of the two channels of the nose) which are not formed nose. Some fishes (Lamprey, Hagfish etc.) have single nostril. In fishes, nostril is used only for smelling, not breathing. In amphibians, nostril is used for smelling and breathing both.
Nose