A puppy's a juvenile dog, the puppy size varies among breeds: smaller puppies may weigh, while others are . All healthy puppies grow quickly after birth. A puppy's coat color may change as the puppy grows older, as's commonly seen in breeds such as the Yorkshire Terrier. In vernacular English, puppy refers specifically to dogs while pup may be used for other mammals such as seals or even rats. Development Born after approximately 61 days of gestation, puppies emerge in an amnion which's bitten… (More on Puppy)