Noun
empty set (plural empty sets)
(set theory) The unique set that contains no elements, denoted ∅ or {}.
I am afraid that mathematics will perish by the end of this century if the present trend for senseless abstractin - as I call it: theory of the empty set - cannot be blocked up. Carl Ludwig Siegel
What I would like to vote for is a candidate that is socially liberal, a fiscal conservative, broadly libertarian with a small l but sensible and pragmatic and with a chance of winning. Thats more or less the empty set. Tyler Cowen
Then this "filter" should possess the following natural structure: 1. Empty set cannot contain anything so it will not belong to our filter. 2. If two subsets, E and F, both might contain "what we are looking for", then so might their intersection. Source: Internet