A short end is a partial roll of unexposed film stock left over during a motion picture production and kept for later use.
If the entire roll has remained unshot and is to be unloaded back into a can, this is not considered a short end, but rather a re-can.
Additionally, particular film stock types might only have been used for a few scenes and thus have considerable short end lengths at the conclusion of their usage.
Short ends are distinct from fresh new rolls because they have often been subject to environmental conditions since leaving their originally sealed can and are no longer under factory warranty, and are generally identified separately to avoid confusion.
Re-cans and short ends are often sold at discounts to lower budget productions by labs, larger production companies, businesses which specialize in their sale, or occasionally still photographers who buy large rolls of film, and load them into their own 35mm canisters.