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Slashed zero; empty set " Ditto mark: Quotation mark: ÷: Division sign: Slash (Solidus) (/), Obelus Dotted circle (Used as a generic placeholder when describing diacritics) Combining Diacritical Marks ⹀ ⸗ Double hyphen: Almost equal to … Ellipsis = Equals sign ℮ Estimated sign! Exclamation mark: Inverted exclamation mark, Interrobang ...
In mathematics, the empty set or void set is the unique set having no elements; its size or cardinality (count of elements in a set) is zero. [1] Some axiomatic set theories ensure that the empty set exists by including an axiom of empty set , while in other theories, its existence can be deduced.
Note that a null set is not necessarily an empty set. Common notations for the empty set include "{}", "∅", and "". The latter two symbols were introduced by the Bourbaki group (specifically André Weil) in 1939, inspired by the letter Ø in the Danish and Norwegian alphabets (and not related in any way to the Greek letter Φ). [2] Empty sets ...
It is a useful concept in analysis, indicating lack of an element where one might be expected. It is usually written with the symbol "∅", in Unicode U+2205 ∅ EMPTY SET (∅, ∅, ∅, ∅). A common ad hoc solution is to use the Scandinavian capital letter Ø instead. There are several kinds of zero:
A mathematical symbol is a figure or a combination of figures that is used to represent a mathematical object, an action on mathematical objects, a relation between mathematical objects, or for structuring the other symbols that occur in a formula.
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In some conventions, [7] the empty set is defined to be a (−1)-simplex. The definition of the simplex above still makes sense if n = −1. This convention is more common in applications to algebraic topology (such as simplicial homology) than to the study of polytopes.