Natural Breed: A breed of dog which occurred naturally without the interference of much selective breeding. This is usually a result of geographical and environmental conditions.

Natural Mutation: A genetic accident which permanently alters certain genetic characteristics.

Natural Selection: The process in nature by which, according to Darwin's theory of evolution, only the organisms best adapted to their environment tend to survive and transmit their genetic characteristics in increasing numbers to succeeding generations while those less adapted tend to be eliminated.

Nausea: A feeling of sickness in the stomach characterized by an urge to vomit.

Neapolitan Mastiff: A large, powerful breed of dog characterized by it's massive head and wrinkled face.

Neck Well Set-On: Good neckline, merging gradually with withers, forming a pleasing transition into topline.

Nesting Behavior: Behavior of a pregnant female who prepares a place to give birth and nurture young.

Neuter: To castrate or spay.

Newfoundland: A breed of large, strong dog developed in Newfoundland and having a thick, usually black coat