Sock is also the term given to the layer of leather or other material covering the insole of a shoe. When only part of the insole is covered, leaving the forepart visible, this is known as a half-sock. The average foot has 250,000 sweat glands, and the average pair gives off about half a pint (almost 250 mL) of perspiration per day. Socks help to absorb this sweat and draw it to areas where air can wick the perspiration away. In cold environments, socks help to retain/remove the moisture given off by one's feet, decreasing the risk of frostbite. There was a shoe worn by Roman comic actors called soccus in Latin. It was a slipper and fitted loosely so it could be taken off quickly.
The invention of a knitting machine in 1589 meant that socks could be knitted six times faster than by hand. Nonetheless, knitting machines and hand knitters worked side by side until 1800.
The next revolution in sock production was the introduction of nylon in 1939. Until then socks were commonly made from silk, cotton and wool. Nylon was the start of blending two or more yarns in the production of socks, a process that still continues.
Other styles of socks include crew socks, mid-calf, and bare socks. A toe sock encases each toe individually the same way a finger is encased in a glove, while other socks have one compartment for the big toe and one for the rest, like a mitten – most notably Japanese tabi. Both of these allow one to wear flip-flops with the socks. Leg warmers, which are not typically socks, are commonly replaced with socks in northern regions of Scandinavia due to the cold climate.
Sock sizes can vary from 8.5 - 11.5 . Sock lengths vary, from ankle-high to thigh level and much in between.
In the UK, a sock's size is the similar to that of a person's foot; for example, a foot that has a shoe size of 9 would require a sock sized 8-10.
In some parts of the world socks are sized differently than shoes. The chart below gives size equivalences, although there is no indication as to which of the numerous sizing systems it represents:
|Sock size||Men's shoe size||Women's shoe size|
|9-11||3-1/2 to 8-1/2||4 to 10|
|10-13||6-1/2 to 12||8-1/2 to 12-1/2|
Other less common sock sizes are 10-15, 13-15, and 13-16.