The empty set symbol stands for the empty set (also written {}). But there is no set here, let alone an empty one.
You are going to have to get over this, because you're wrong. The empty set symbol is used in linguistics for the purpose described. The Danish letter Ø is not used for this purpose except as a font hack when a proper slashed circle is unavailable.
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Michael Everson * * Everson Typography * * http://www.evertype.com
