Look up envelope in Wiktionary, the free dictionary.

An envelope is the paper container used to hold a letter being sent by post.

Envelope may also refer to:

Mathematics

• Envelope (mathematics), a curve, surface, or higher-dimensional object defined as being tangent to a given family of lines or curves (or surfaces, or higher-dimensional objects, respectively)
• Envelope (category theory)

Science

• Viral envelope, the membranal covering surrounding the capsid of a virus
• Cell envelope of a bacterium, consisting of the cell membrane, cell wall and outer membrane
• Airship § Envelope, the fabric skin covering the airship
• Building envelope, the exterior layer of a building that protects it from the elements
• Envelope (motion), a solid representing all positions that an object may occupy during its normal range of motion
• Envelope (music), the variation of a sound over time, as is used in sound synthesis
• Envelope (radar), the volume of space where a radar system is required to reliably detect an object
• Envelope (waves), a curve outlining the peak values of an oscillating waveform or signal
• Envelope detector, an electronic circuit used to measure the envelope of a waveform
• Flight envelope, the limits within which an aircraft can operate

Entertainment

• Envelopes (band), an indie/pop band from Sweden and France, based in the UK
• Envelope (film), a 2012 film
• "Envelopes", a song by Frank Zappa from his 1982 album Ship Arriving Too Late to Save a Drowning Witch

Other uses

• Envelope (military), attacking one or both of the enemy's flanks to encircle the enemy
• The envelope of an internet email, its SMTP routing information
• Envelope system, a method of personal budgeting where money is allocated for specific purposes
• Gaza envelope, a region in southwestern Israel adjacent to the Gaza Strip

See also

• Two envelopes problem, a paradox
• Stellar envelope (disambiguation), for astrophysics uses