Question: Which dog breed is larger, Whippets or Jack Russell Terriers?

Context articles: American Russell Terrier Club
Soft mouth
Fox Terrier
Whippet
Jack Russell Terrier
Feist (dog)
Russell Terrier
Breed standard (dogs)
Parson Russell Terrier
Jack Russell Terrier Club of America

The American Russell Terrier Club (formerly named the English Jack Russell Terrier Club), founded by JoAnn Stoll in 1995, was the first registry in the United States to maintain the Russell Terrier as a separate breed from the Parson Russell Terrier.
 The American Jack Russell Terrier Club is affiliated with both the United Kennel Club and the American Kennel Club.
 The purpose of the early founders was to establish a registry for the perpetuation and development of the Russell Terrier as a pure strain of working Jack Russell Terrier keeping their blood and type pure within the registry to works towards Kennel Club recognition as an official breed in the US.
 On January 1, 2001, the United Kennel Club recognized the Russell Terrier as an official breed, designating only the stock from the American Russell Terrier Club as Foundation stock for the UKC Russell Terrier.
 In 2004 the American Russell Terrier Club submitted an official request to include the American Russell Terrier Club stock into the AKC FSS Program to work towards becoming an official breed under the perimeters.
 On December 8, 2004, the AKC officially accepted the Russell Terrier.
The term soft mouth is used by breeders and users of hunting dogs to refer to a behavioral tendency to pick up, hold, and carry quarry gently.
 It is not a preferred characteristic of terriers and ratters, who are expected to roughly shake and mangle pests such as rats and snakes in order to kill them quickly and efficiently.
 It is desirable in gundogs such as retrievers and spaniels which are expected to produce quarry intact and in good condition, and is a notoriously difficult behavior to teach to a dog without an inborn temperament to do so.
 As a result, breeders and users of gun dogs arrived on this term to describe a characteristic important to this enterprise.
 Dogs breeds known for producing more soft-mouthed individuals include Golden Retrievers, Cocker Spaniels, Poodles, and Gordon Setters, but in any litter some individuals may be much less soft-mouthed than others, as there may be relatively soft-mouthed individuals in a litter of even classically hard-mouthed breeds such as Jack Russell Terriers or Mastiffs.
Fox Terriers are two different breeds of the terrier dog type: the Smooth Fox Terrier and the Wire Fox Terrier.
 Both of these breeds originated in the 19th century from a handful of dogs who are descended from earlier varieties of British terriers, and are related to other modern white terrier breeds.
 In addition, a number of breeds have diverged from these two main types of fox terrier and have been recognised separately, including the Jack Russell Terrier, Miniature Fox Terrier and Rat Terrier.
 The Wire and Smooth Fox Terriers share similar characteristics, the main differences being in the coat and markings.
 They have been successful in conformation shows, more prominently in America than their homeland.
The Whippet (also English Whippet or Snap dog) is a dog breed of medium-size.
 They are a sighthound breed that originated in England, where they descended from greyhounds. Whippets today still strongly resemble a smaller greyhound.
 Shown in the Hound group, Whippets have relatively few health problems other than arrhythmia.
 Whippets also participate in dog sports such as lure coursing, agility, and flyball.
 The name is derived from an early 17th-century word, now obsolete, meaning to "move briskly".
The Jack Russell Terrier is a small terrier that has its origins in fox hunting.
 It is principally white-bodied and smooth, rough or broken-coated but can be any colour.
A Feist is a small hunting dog, descended from the terriers brought over to the United States by English miners and other working class immigrants.
 These terriers probably included crosses between the Smooth Fox Terrier, the Manchester Terrier and the now extinct English White Terrier.
 These dogs were used as ratters, and gambling on their prowess in killing rats was a favorite hobby of their owners.
 Some of these dogs have been crossed with Whippets or Italian Greyhounds (for speed) and Beagles (for hunting ability) - extending the family to include a larger variety of purpose than the original ratter, or Rat Terrier.
The Russell Terrier is a predominantly white working terrier with an instinct to hunt prey underground.
 The breed was derived from the Reverend John Russell's working terrier strains that were used in the 19th century for fox hunting.
 The Reverend's fox working strains were much smaller than the Show Fox Terrier and remained working terriers.
 The size of the Russell Terrier (10″ to 12″) combined with a small flexible, spannable chest makes it an ideal size to work efficiently underground.
 Their unique rectangular body shape with the body being of slightly longer length than the leg makes them distinctly different from the Parson Russell Terrier and the JRTCA Jack Russell Terrier.
A breed standard (also called bench standard or the standard) in the dog fancy is a set of guidelines covering specific "externally observable" qualities such as "appearance", "movement", and "temperament" for that dog breed.
 Breed standards are not scientific documents, but are written for each breed by clubs of hobbyists called breed clubs for their own specific requirements.
 Details and definitions within breed standards for a specific dog breed may vary from breed club to breed club and from country to country.
 Dog breed standards are similar in form and function to breed standards for other domesticated animals.
The Parson Russell Terrier is a breed of small white terrier that was the original Fox Terrier of the 18th century.
 The breed is named after the person credited with the creation of this type of dog, the Reverend John "Jack" Russell.
 It is the recognised conformation show variety of the Jack Russell Terrier and was first recognised in 1990 in the United Kingdom as the Parson Jack Russell Terrier.
 In America, it was first recognised as the Jack Russell Terrier in 1997.
 The name was changed to its current form in 1999 in the UK and by 2008 all international kennel clubs recognised it under the new name.
The Jack Russell Terrier Club of America (JRTCA) is the largest Jack Russell Terrier club and registry in the world, and is the National Breed Club and Registry for the Jack Russell Terrier in the United States.