Push the envelope

[Fred Shapiro]

On Tue, 25 Jul 2000, Paul McFedries wrote:

> In any case, it seems to me that all you've done is restated the definition
> of "push (the edge of) the envelope." I guess what I'm really interested in
> is the root of the "envelope" metaphor. Why is the set of limitations for an
> aircraft (or of any technological system) called an "envelope"?

Envelope = boundary.  The term derives from mathematics, where "envelope"
means the outer boundary of a family of curves.


Fred R. Shapiro                             Coeditor (with Jane Garry)
Associate Librarian for Public Services     TRIAL AND ERROR: AN OXFORD
  and Lecturer in Legal Research            ANTHOLOGY OF LEGAL STORIES
Yale Law School                             Oxford University Press, 1998
e-mail: fred.shapiro at yale.edu               ISBN 0-19-509547-2