Let 
be a map. Then
is expansive if the statement that
the distance 
for all 
implies that 
. Equivalently, 
is expansive if the orbits of two points 
and 
are never very close.
Expansive
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Cite this as:
Weisstein, Eric W. "Expansive." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Expansive.html