AAFCO (The Association of Animal Feed Control Officials): This group defines the terms used on dog-food packaging, such as “by-products” and “meat meal.”

AKC (The American Kennel Club): the oldest and largest registry of purebred dogs in the United States.

Amino acids: The building blocks of proteins. Dogs require 10 specific amino acids for a complete diet and good health.

Bite: The way the teeth of the upper jaw meet the teeth of the lower jaw. With a level bite, the teeth meet edge to edge. With a scissors bite, the lower teeth slide just behind the upper teeth.

Buster Cube: A food puzzle activity toy for dogs. It's a cube with a maze of tunnels inside. You pour in some kibble and turn the cube around, and the dog then has to move the cube about to get some pieces of food to dribble out.

Collapsing trachea: A tendency of the windpipe to collapse in on itself, often due to a failure of the cartilage rings to develop properly. The condition can be worsened through pressure on the throat, as from a collar.

Color dilution alopecia: Alopecia is hair loss. Color dilution is the fading of what would be a black coat to the blue of the Yorkshire terrier. Color dilution can be a genetic cause of alopecia.

Dewclaws: The extra “toes” often seen on dogs a short distance up the leg from the foot.

Docking: The artificial shortening of the dog's tail via surgery, usually done when puppies are very young.

Duck dryer: A hair dryer specifically meant for dogs, with a stand to leave your hands free and only low heat to keep your dog safe.

Dysplasia: Faulty development of a joint, most often a hip.

Enzymatic cleanser: A cleaning agent specifically meant to counteract the smells of urine or feces, so the dog is not attracted back to the same spot.

Exercise pen: A portable enclosure that collapses flat and opens to a rectangle or circle, and that can be used as a playpen. Most often seen in heavy wire, but also available with aluminum framing and mesh panels.

Forced-air dryer: A dryer that uses a powerful blast of air to blow water out of the hair rather than heat to evaporate it.

Group judging: The best dogs representing each breed in a single group, such as the Toy Group, are brought together and the top four dogs are chosen. Best in Group goes on to compete for Best in Show.

Harshness: A coat quality, undesirable in a Yorkshire terrier, of roughness or coarseness. Wirehaired terriers should have harsh coats. A Yorkie's coat should be silky.

Heat: The twice-yearly estrus of the female dog, generally lasting about three weeks each time it occurs, during which she is both highly attractive to males and sexually receptive.

KC: Britain's Kennel Club, known simply as “the” kennel club.

Kong: A hard rubber toy, shaped like a pinecone, with a hollow core that can be stuffed with various food treats.

Major: A dog show win over a sufficient number of dogs to earn three or more points. The number of dogs varies by breed and area of the country.

Microchip: A glass-encased computer chip the size of a grain of rice, injected into the dog's shoulder muscle as an identification device. The unique number can be read by a scanner passed over the dog's body.

Pancreatitis: An inflammation of the pancreas, often caused by eating foods high in fats.

Papers: Certificate necessary to register a dog with the AKC or other registry, attesting to the dog's purebred parentage.

Patellar luxation: The slipping of the patella, or kneecap, out of the joint in which it should be seated. Severity of the slippage varies.

Performance sports: Dog competitions other than the conformation ring, including agility, obedience, tracking, and others.

Pica: The eating of nonfood items, such as rocks or cloth.

Piddle pads: Absorbent rectangles of material intended to be provided as a surface for elimination.

Polydipsia/polyuria: Increased drinking of water and increased urination, often in association with diabetes or renal failure.

Portosystemic shunt: Blood vessel bypassing the liver, which ordinarily closes off to direct blood through the liver when puppies are young. Failure to close requires surgical intervention. Genetics can predispose a Yorkshire terrier to shunt problems.

Separation anxiety: Elevated stress over being left alone or separated from a specific person. Can result in destructive behavior, constant vocalization. Requires a program of behavior modification.

Standard: The written description of a breed, provided by the parent club of a breed.

Toy group: AKC-defined group of dog breeds to which the Yorkshire terrier belongs, consisting completely of small dogs.

Withers: The highest point of the shoulder, which can be felt just below and to the side of the base of the neck. Point at which a dog's height is measured.

Wrappings: Papers and rubber bands into which a Yorkshire terrier's coat is rolled to keep it from being soiled or broken.