German Shepherd Dog — The full breed name, often abbreviated to GSD.

GSD — The common abbreviation for German Shepherd Dog.

Alsatian — The historic name widely used for the German Shepherd Dog in Britain during much of the twentieth century. It refers to the same breed, not a separate variety.

Alsatian Wolf Dog — The name adopted for the breed in Britain after the First World War. "Wolf Dog" was later removed because it encouraged the mistaken belief that the breed was a wolf hybrid.

Deutscher Schäferhund — The German name for the German Shepherd Dog. It translates directly as "German Shepherd Dog".

Horand von Grafrath — The first registered German Shepherd Dog and an important foundation dog in the development of the breed.

Max von Stephanitz — The German cavalry officer and breed founder most closely associated with establishing the German Shepherd Dog and promoting its development as a versatile working breed.

Foundation dog — An early dog whose descendants contributed significantly to the establishment of a breed or population.

Popular sire effect — A reduction in genetic diversity that can occur when one successful male is used extensively and appears repeatedly across later pedigrees.

Working line — German Shepherds bred primarily for working performance, drive and task ability rather than conformation showing.

Show line — German Shepherds bred partly toward the conformation breed standard while still requiring correct temperament and function.

West German working line — A working-line population associated with West German breeding traditions; a label of ancestry, not a certified behaviour type.

West German show line — A show-line population associated with West German breeding traditions; lines vary within the group.

Czech line — A working-line population associated with Czech breeding traditions; labels describe ancestry, not guaranteed temperament.

DDR line — Refers to former East German breeding; modern pedigrees may combine populations, so the label is not a behaviour guarantee.

American/Canadian show line — A show-line population associated with North American breeding; individual dogs vary widely.

Stock coat — The standard short-to-medium double coat with undercoat; a recognised variety.

Long stock coat — The longer outer-coat variety, also with an undercoat; a recognised variety.

Double coat — A coat with a protective outer guard layer and a soft undercoat; should not usually be shaved.

Undercoat — The soft dense layer beneath the guard hairs that sheds heavily twice a year.

Sable — A coat pattern with banded hairs giving a wolf-like appearance; common in working lines.

Bi-colour — A coat pattern, predominantly black with limited tan markings.

Black and tan — A classic coat pattern with black over the saddle and tan on the legs and face.

Black and red — A common show-line colour variant with deep red markings instead of tan.

Solid black — An all-black coat; a recognised German Shepherd colour, not a separate breed.

Drive — The intensity and persistence with which a dog pursues a goal; varies between individuals.

Arousal — Nervous-system activation; not automatically excitement or aggression.

Threshold — The point at which a dog can no longer process or respond normally.

Reactivity — An intensified response to a trigger; a description of behaviour, not a diagnosis.

Aggression — Behaviour intended to threaten or cause harm; has many causes and is not a breed trait.

Socialisation — Positive, gradual exposure that builds calm capability — not simply meeting everyone.

Habituation — Becoming accustomed to normal stimuli through safe, repeated experience.

Sensitisation — Becoming more reactive to a stimulus through repeated or overwhelming exposure.

Trigger stacking — The accumulation of several stresses without enough recovery.

Reinforcement — Anything that makes a behaviour more likely to happen again.

Marker — A signal (such as "YES") that identifies the exact successful moment.

Decompression — The gradual process of a new or stressed dog settling into safety.

Bite inhibition — The learned ability to control the pressure of the mouth.

Body condition — How a dog's weight and shape look and feel; a better guide than scale weight.

Hip score — A radiographic assessment of hip joint conformation under the BVA/Kennel Club scheme.

Elbow grade — A radiographic assessment of elbow joint conformation under the BVA/Kennel Club scheme.

DM status — The result of a DNA test for the degenerative myelopathy variant; "at risk" is not a diagnosis.

Genotype — The genetic variants a dog carries, including hidden ones.

Phenotype — What can actually be seen or measured in the dog.

Carrier — A dog carrying one copy of a recessive variant without showing it.

Coefficient of inbreeding — An estimate of the probability that gene copies came from common ancestors.