Definition of envelope in English:


Pronunciation: /ˈenvəˌlōp//ˈänvəˌlōp/


  • 1A flat paper container with a sealable flap, used to enclose a letter or document.

    • ‘New product areas would include drawing paper, envelopes, greetings cards and stationary folders.’
    • ‘To maintain secrecy, the return ballot paper envelope had a detachable flap on which the voter filled in their details.’
    • ‘Returning envelopes containing ballot papers are also distinctively marked to aid sorting.’
    • ‘They are all instant communications that are far less bother than putting pen to paper, finding an envelope, licking the flap, sticking on a stamp and popping it in a post box.’
    • ‘The soldier would then enclose his ballot and the thrice-signed document in an envelope.’
    • ‘It is enclosed in a sealed envelope along with this letter.’
    • ‘The paperwork involved is horrendous - ballot papers, witness forms, pre-paid envelopes, ballot paper envelopes and explanatory notes.’
    • ‘Each letter had a small number in the corner on the backside of the letter; in the envelope was just paper, nothing else.’
    • ‘My boss handed me the envelope containing the necessary papers.’
    • ‘Residents will have until January 6 to return the ballot paper in the pre-paid envelope which will come with the letter.’
    • ‘Completed questionnaires were mailed back to the research team in self-addressed, stamped envelopes enclosed with the surveys.’
    • ‘For years, the yellowing envelope and the letter it contained were kept solely for nostalgia value, despite being pressed into service as a humble bookmark.’
    • ‘She was typing letters, envelopes and handwriting appointments onto paper planners that were stuffed in ragged edged file folders.’
    • ‘In the latest incident, at 12.30 pm on Sunday, a 93-year-old woman had a brown envelope containing documents stolen.’
    • ‘The pens and pencils were in a can on the corner, a small box contained crisp white envelopes, extra paper was in a folder, and a stack of manuscripts sat on the far side of the desk.’
    • ‘What made it worse was they had not paid enough postage for the weight of paper the envelopes contained.’
    • ‘Each survey was enclosed in a stamped envelope, addressed to the researcher.’
    • ‘Many of those in the line clutched envelopes containing documents such as birth and marriage certificates, along with photographs.’
    • ‘Declined manuscripts will be returned if stamped, self-addressed envelopes are enclosed with submissions.’
    • ‘The letters contained a smaller envelope each, with the defendant's name on three of these and a further two names on the other two.’
    wrapper, wrapping, wrap, sleeve, cover, covering
    casing, case
    View synonyms
  • 2A covering or containing structure or layer.

    ‘the external envelope of the swimming pool’
    • ‘Construction of the house commenced on-site on October 14 and the structural envelope was erected in an incredible five days.’
    • ‘Its strong external envelope, made from several distinct Titanium shells, will protect it from the dangers of a long flight in space's hostile environment.’
    • ‘The bones of the ankles and feet also took on a paddle shape, and individual digits were closely packed within a streamlining envelope of soft tissue.’
    • ‘In this approach they have the patient stay within the envelope and only use a comfortable range of energy expenditure.’
    • ‘Then I fly the boom around to make sure it can fly within the prescribed envelope.’
    • ‘We checked in with the frigate, made sure her winds were within our approach envelope, and landed at 0757.’
    • ‘This provides a visually intricate envelope to the external public space and assists night-time security to the main entrance.’
    • ‘A sea-urchin egg is surrounded by a protective covering known as the vitelline envelope, which in turn is covered with a thick coat of jelly.’
    • ‘In summer the fan is reversed, cooling the building by drawing fresh air through louvres in the external envelope.’
    • ‘The observed tide is a result of the rotation of the Earth within the envelope of the two deformations, which remain fixed in orientation relative to the Moon and Sun.’
    • ‘Concrete grade beams spanning between the caissons were used to accommodate external envelope conditions and elevator pits.’
    • ‘In addition to serving as a semipermeable layer, the envelope in cucumber, muskmelon, and other cucurbitaceous seeds is known to act as the primary barrier to radicle emergence.’
    • ‘Providers know that they have to work within the envelope of resources earned by the insurance plan.’
    • ‘Suppose the atmosphere of our planet to be surrounded by an envelope impervious to light, with an aperture on the sunward side, through which a solar beam could enter and cross our atmosphere.’
    • ‘The laboratory blocks within the overall envelope are linked by walkways, bridges and meeting platforms.’
    • ‘Located at the outer edges of the building and formed by the external envelope, these lofts are moulded by folds that are conspicuous both inside and out.’
    • ‘No one can do any work within the structural envelope of the building.’
    • ‘It was however still possible to tell the location of the nuclear envelope to within 1-2 m.’
    • ‘‘I wanted to hint at the modern interior that's behind the historic external envelope,’ he says.’
    • ‘But it is noticeable that, even within the overall envelope of European culture, it is all too easy for despotism, of one sort or another, to become the ruling paradigm.’
    1. 2.1 The outer metal or glass housing of a vacuum tube, electric light, etc.
      • ‘As you know from replacing light bulbs, there is a large, thin, frosted glass envelope in the familiar light bulb shape.’
      • ‘The glass envelope gently undulates to follow the site as it moves along the riverfront; it seems to express the flow of the water.’
      • ‘The other great problem of glass envelopes is their transparency not only to light, but to much of the electro-magnetic spectrum.’
      • ‘The presumption that the glass envelopes of these bulbs function as cutoff filters to remove short wavelength radiation was unsubstantiated.’
      cover, case, shell, sheath, sheathing, wrapper, wrapping, sleeve, jacket, housing, capsule, folder
      View synonyms
    2. 2.2 The structure within a balloon or nonrigid airship containing the gas.
      • ‘They hold open the envelope as the balloon is inflated.’
      • ‘The team plays an important role in ensuring the balloon is prepared and filled to suit the timing of the launch and to ensure the envelope is ready for take off.’
      • ‘At this time of day, the world is wonderfully peaceful - just the sound of distant burners pushing hot air into the envelopes of nearby balloons and songbirds below.’
      • ‘He led a team of 12 in Glastonbury, which designed and built the balloon envelope and flight platform.’
    3. 2.3Microbiology A membrane forming the outer layer of certain viruses.
      • ‘The departing viruses therefore have an envelope that can fuse with the membranes of nearby cells, allowing the virus to enter.’
      • ‘The cell envelope of gram-positive bacteria consists of the cytoplasmic membrane and a cell wall.’
      • ‘Evidence suggesting the existence of multiple import pathways at the outer envelope membrane for different classes of precursor proteins has been presented.’
      • ‘The insertion of the fusion peptide in the host membrane provides the necessary link between the viral envelope and the cell membrane.’
      • ‘As the infection progresses, however, each sequential form of the virus envelope increasingly escapes detection.’
    4. 2.4Electronics A curve joining the successive peaks of a modulated wave.
      • ‘Noise, when used with a vocal modulator, traces the envelope of the vocal with wideband noise.’
    5. 2.5Mathematics A curve or surface tangent to each of a family of curves or surfaces.
      • ‘To compare the deuterium contents of the different peptides, an averaged mass was obtained by centroiding the envelope of isotopic peaks.’
      • ‘Jacob Bernoulli also discovered a general method to determine evolutes of a curve as the envelope of its circles of curvature.’
      • ‘We looked at it, and it's just a sine wave, an envelope of minimum and maximum, with the width of the wave showing the time in boom vs. the time in recession.’
      • ‘In particular he constructed the tangent plane and exhibited the surface as an envelope of planes.’
      • ‘The idea of an envelope of a family of lines had not been mentioned either.’
    6. 2.6Astronomy The nebulous covering of the head of a comet; coma.
      • ‘These circumstellar envelopes are indeed progenitors of planetary nebulae.’


Mid 16th century (in the sense wrapper, enveloping layer): from French enveloppe, from envelopper envelop The sense covering of a letter dates from the early 18th century.