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 , 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