The term annihilator is used in several different ways in various aspects of mathematics. It is most commonly used to mean the set of all functions satisfying a given set of conditions which is zero on every member of a given set.
Annihilator
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Cite this as:
Weisstein, Eric W. "Annihilator." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Annihilator.html