A unilateral shift is a weighted shift 
for which 
for all 
.
Unilateral Shift
See also
Weighted ShiftThis entry contributed by Mohammad Sal Moslehian
Explore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W., with contributions by Mohammad Sal Moslehian. "Unilateral Shift." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/UnilateralShift.html