envelope
/ˈɛnvə(ˌ)loʊp/ noun A2- A paper or cardboard wrapper used to enclose small, flat items, especially letters, for mailing.
- Something that envelops; a wrapping.
- A bag containing the lifting gas of a balloon or airship; fabric that encloses the gas-bags of an airship.
- A mathematical curve, surface, or higher-dimensional object that is the tangent to a given family of lines, curves, surfaces, or higher-dimensional objects.
- A curve that bounds another curve or set of curves, as the modulation envelope of an amplitude-modulated carrier wave in electronics.
- The shape of a sound, which may be controlled by a synthesizer or sampler.
- The information used for routing a message that is transmitted with the message but not part of its contents.
- An enclosing structure or cover, such as a membrane; a space between two membranes
Plural envelopes
From the library
He leaned upon his hand, with his untasted breakfast before him, and he stared at the slip of paper which he had just drawn from its envelope.
Then he took the envelope itself, held it up to the light, and very carefully studied both the exterior and the flap.
“Your native shrewdness, my dear Watson, that innate cunning which is the delight of your friends, would surely prevent you from inclosing cipher and message in the same envelope.
“The same writing,” remarked Holmes, as he opened the envelope, “and actually signed,” he added in an exultant voice as he unfolded the epistle.
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