The American Kennel Club (AKC) registers American Pit Bull Terriers under the name American Staffordshire Terrier. According to the AKC, the Pit Bull Terrier was developed in England and called the Staffordshire Terrier, which is the source of the name used by the AKC to refer to this breed.
The United Kennel Club (UKC) registers Pit Bull Terriers under the name American Pit Bull Terrier. The UKC allows AKC-registered American Staffordshire Terriers to be registered as UKC American Pit Bull Terriers. The breed standards for AKC American Staffordshire Terriers and UKC American American Pit Bull Terriers are practically identical other than the name of the breed.