Simple Definition of envelope
: an enclosing cover for a letter, card, etc.
Full Definition of envelope
1 : a flat usually paper container (as for a letter)
3 a : the outer covering of an aerostat b : the bag containing the gas in a balloon or airship
4 a : a natural enclosing covering (as a membrane, shell, or integument) b : a lipoprotein unit membrane that forms the outer layer of some virions
5 a : a curve tangent to each of a family of curves b : a surface tangent to each of a family of surfaces
6 : a set of performance limits (as of an aircraft) that may not be safely exceeded; also : the set of operating parameters that exists within these limits
7 : a conventionally accepted limit <new computers that push the envelope>
Usage Discussion of envelope
The \ˈen-\ and \ˈän-\ pronunciations are used with about equal frequency, and both are fully acceptable, though the \ˈän-\ version is sometimes decried as “pseudo-French.” Actually \ˈän-\ is exactly what one would expect to hear when a French word like entrepreneur is becoming anglicized. Envelope, however, has been in English for nearly 300 years, plenty of time for it to become completely anglicized and for both of its pronunciations to win respectability.
First Known Use of envelope
ENVELOPE Defined for Kids
Definition of envelope for Students
: a flat usually paper container (as for a letter)
Medical Definition of envelope
: a natural enclosing covering (as a membrane or integument); especially : a lipoprotein unit membrane that forms the outer layer of some virions and surrounds the viral capsid <These glycoprotein complexes, swept up by the budding virus as it acquires its envelope, are crucial to HIV's ability to infect new cells.—William A. Haseltine et al., Scientific American, October 1988>
Seen and Heard
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