"Applehead" Chihuahuas weigh six pounds or less at maturity. The phrase "apple head" refers to the preferred shape of the canine's head. According to the American Kennel Club, the official standard for the breed dictates that the dogs have round, domed apple-shaped heads.
In contrast to "applehead" Chihuahuas are "deer head" dogs of the breed. These dogs have longer muzzles and a skull that is flatter on top. Dogs with this shape of head do not meet the AKC's breed standard for Chihuahuas.
Chihuahuas also come in long-haired and short-haired varieties, both allowed under the AKC standard. Occasionally breeders produce dogs they refer to as "teacup" Chihuahuas. These dogs are a small variant of the breed.