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  2. Empty set - Wikipedia

    en.wikipedia.org/wiki/Empty_set

    A symbol for the 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 (U+00D8 Ø LATIN CAPITAL LETTER O WITH STROKE) in the Danish and Norwegian alphabets. [2]

  3. Null sign - Wikipedia

    en.wikipedia.org/wiki/Null_sign

    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 ...

  4. Ø - Wikipedia

    en.wikipedia.org/wiki/Ø

    The letter "Ø" is sometimes used in mathematics as a replacement for the symbol "∅" (Unicode character U+2205), referring to the empty set as established by Bourbaki, and sometimes in linguistics as a replacement for same symbol used to represent a zero.

  5. Zero (linguistics) - Wikipedia

    en.wikipedia.org/wiki/Zero_(linguistics)

    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:

  6. Null (mathematics) - Wikipedia

    en.wikipedia.org/wiki/Null_(mathematics)

    In set theory, the empty set, that is, the set with zero elements, denoted "{}" or "∅", may also be called null set. [3] [5] In measure theory, a null set is a (possibly nonempty) set with zero measure. A null space of a mapping is the part of the domain that is mapped into the null element of the image (the inverse image of the null element).

  7. Axiom of empty set - Wikipedia

    en.wikipedia.org/wiki/Axiom_of_empty_set

    Furthermore, one sometimes considers set theories in which there are no infinite sets, and then the axiom of empty set may still be required. However, any axiom of set theory or logic that implies the existence of any set will imply the existence of the empty set, if one has the axiom schema of separation. This is true, since the empty set is a ...

  8. Empty Mailbox in AOL Mail

    help.aol.com/articles/empty-mailbox-in-aol-mail

    Are your emails and contacts missing? If you haven't signed in to AOL Mail for 12 months or more, your mailbox is considered inactive. An inactive mailbox stops receiving new emails, and all mailbox contents, folders, contacts and settings are permanently deleted.

  9. Greek letters used in mathematics, science, and engineering

    en.wikipedia.org/wiki/Greek_letters_used_in...

    Alternative symbol for a wave function in quantum mechanics; Note: The empty set symbol ∅ looks similar, but is unrelated to the Greek letter. or represents: the golden ratio 1.618... in mathematics, art, and architecture; Euler's totient function in number theory