A ski is a narrow strip of semi-rigid material worn underfoot to glide over snow. Substantially longer than wide and characteristically employed in pairs, skis are attached to ski boots with ski bindings, with either a free, lockable, or partially secured heel. For climbing slopes, ski skins (originally made of seal fur, but now made of synthetic materials) can be attached at the base of the ski.Originally intended as an aid to travel over snow, they are now mainly used recreationally in the sport of skiing.The word ski comes from the Old Norse word skíð which means "cleft wood",[1] "stick of wood" or "ski".[2] In Old Norse common phrases describing skiing were fara á skíðum (to travel, move fast on skis), renna (to move swiftly) and skríða á skíðum (to stride on skis).[3] In modern Norwegian the word ski has largely retained the Old Norse meaning in words for split firewood, wood building materials (such as bargeboards) and roundpole fence.[4][5][6] In Norwegian this word is usually pronounced [ˈʂiː]. In Swedish, another language evolved from Old Norse, the word is skidor (plural, pronounced [ˈɧîːdʊr]; singular: skida). [Wikipedia]