envelope

n. paper wrapper in which letters are sealed and sent

An envelope is a packaging product, usually made of flat, planar material such as paper or cardboard, and designed to contain a flat object, which in a postal-service context is usually a letter or card. The traditional type is made from a sheet of paper cut to one of three shapes: the rhombus (also referred to as a lozenge or diamond), the short-arm cross, and the kite. These designs ensure that in the course of envelope manufacture when the sides of the sheet are folded about a delineated central rectangular area, a rectangular-faced, usually oblong, enclosure is formed with an arrangement of four flaps on the reverse side, which, by virtue of the shapes of sheet traditionally used, is inevitably symmetrical.
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Noun
1. a flat rectangular paper container for papers
(hypernym) container
(hyponym) window envelope
2. any wrapper or covering
(hypernym) wrapping, wrap, wrapper
3. a curve that is tangent to each of a family of curves
(hypernym) curve, curved shape
4. a natural covering (as by a fluid); "the spacecraft detected an envelope of gas around the comet"
(hypernym) covering, natural covering, cover
5. the maximum operating capability of a system; "test pilots try to push the envelope"
(hypernym) operating capability, performance capability
6. the bag containing the gas in a balloon
(synonym) gasbag
(hypernym) bag
(part-holonym) balloon

n. cover, envelope

(n.)
Alt. of Envelop