(noun.) any wrapper or covering.
(noun.) a flat (usually rectangular) container for a letter, thin package, etc..
(noun.) the bag containing the gas in a balloon.
(noun.) the maximum operating capability of a system (especially an aircraft); 'test pilots try to push the envelope'.
(noun.) a natural covering (as by a fluid); 'the spacecraft detected an envelope of gas around the comet'.
(noun.) a curve that is tangent to each of a family of curves.
伯娜丁整理
卡尔文校对