envelopes

Noun

envelope (plural envelopes)

1. A paper or cardboard wrapper used to enclose small, flat items, especially letters, for mailing.
   • Now we are liberal with our innermost secrets, spraying them into the public ether with a generosity our forebears could not have imagined. Where we once sent love letters in a sealed envelope, or stuck photographs of our children in a family album, now such private material is despatched to...2013 June 14, Jonathan Freedland, “Obama's once hip brand is now tainted”, in The Guardian Weekly, volume 189, number 1, page 18
2. Something that envelops; a wrapping.

   Synonyms:

   wrapper

3. A bag containing the lifting gas of a balloon or airship; fabric that encloses the gas-bags of an airship.
   • They have no internal or external support structure, being simply a fabric bag (or envelope) filled with a lighter than air gas. Inside the envelope are one or more "ballonets", or smaller bags, which help maintain the envelope's shape.1992, Lieutenant Colonel Donald E. Ryan, Jr, The airship's potential for intertheater and intratheater airlift, DIANE Publishing, page 46

   Synonyms:

   gasbag

4. A mathematical curve, surface, or higher-dimensional object that is the tangent to a given family of lines, curves, surfaces, or higher-dimensional objects.
5. A curve that bounds another curve or set of curves, as the modulation envelope of an amplitude-modulated carrier wave in electronics.
6. The shape of a sound, which may be controlled by a synthesizer or sampler.

See all 12 meanings of envelope