A jersey is an item of knitted clothing

Clothing

Clothing refers to any covering for the human body that is worn. The wearing of clothing is exclusively a human characteristic and is a feature of nearly all human societies...

, traditionally in wool

Wool

Wool is the textile fiber obtained from sheep and certain other animals, including cashmere from goats, mohair from goats, qiviut from muskoxen, vicuña, alpaca, camel from animals in the camel family, and angora from rabbits....

 or cotton

Cotton

Cotton is a soft, fluffy staple fiber that grows in a boll, or protective capsule, around the seeds of cotton plants of the genus Gossypium. The fiber is almost pure cellulose. The botanical purpose of cotton fiber is to aid in seed dispersal....

, with sleeve

Sleeve

Sleeve is that part of a garment which covers the arm, or through which the arm passes or slips. The pattern of the sleeve is one of the characteristics of fashion in dress, varying in every country and period...

s, worn as a pullover

Sweater

A sweater, jumper, pullover, sweatshirt, jersey or guernsey is a garment intended to cover the torso and arms. It is often worn over a shirt, blouse, T-shirt, or other top, but may also be worn alone as a top...

, as it does not open at the front, unlike a cardigan

Cardigan (sweater)

A cardigan is a type of machine- or hand-knitted sweater that ties, buttons or zips down the front; by contrast, a pullover does not open in front but must be "pulled over" the head to be worn. The cardigan was named after James Brudenell, 7th Earl of Cardigan, a British military commander,...

. It is usually close-fitting and machine knitted in contrast to a guernsey

Guernsey (clothing)

A guernsey, or gansey, is a seaman's knitted woollen sweater, similar to a jersey, which originated in the Channel Island of the same name.-Origins:...

 that is more often hand knit with a thicker yarn

Yarn

Yarn is a long continuous length of interlocked fibres, suitable for use in the production of textiles, sewing, crocheting, knitting, weaving, embroidery and ropemaking. Thread is a type of yarn intended for sewing by hand or machine. Modern manufactured sewing threads may be finished with wax or...

. The word is usually used interchangeably with sweater

Sweater

A sweater, jumper, pullover, sweatshirt, jersey or guernsey is a garment intended to cover the torso and arms. It is often worn over a shirt, blouse, T-shirt, or other top, but may also be worn alone as a top...

 and is the name always officially used in the United Kingdom

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 to refer to the item when worn as part of the uniform of military, police or other uniformed personnel.