A puppy is a juvenile dog, generally less than one year of age that has not reached sexual maturity. The term is sometimes abbreviated to pup, a term also used for the offspring of wolves.
Puppy size varies among breeds, smaller puppies may weigh 1–3 lbs, while others are 15–20 lbs. All healthy puppies grow rapidly after birth.
Reputable dog breeders raise their animals in humane conditions, provide good socialization and often formal training, and adhere to the breed standard. They are knowledgeable about major health problems associated with their breed, and with the principles of genetics, frequently undertaking specific matings to produce or refine particular desirable characteristics in their dogs. Less than scrupulous breeding operations, known as puppy mills, may provide less attention to genetics, prenatal care, and nutrition, and often produce puppies which are improperly socialized and in poor health.