RE: IPA Null Consonant

From: Jim Allan (
Date: Wed May 28 2003 - 20:44:40 EDT

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    Kent Karlsson posted:

    > And I (still!) very strongly disagree. The empty set symbol stands
    > for the empty set (also written {}). But there is no set here, let alone
    > an empty one. Possibly an empty string (of phonetic symbols?).
    > Written as '' or "" in your favourite programming language, and
    > conventionally written as a lowercase epsilon (ε) in math contexts.
    > (That does not make the empty string equal to a string consisting
    > of the letter ε, of course!)

    No one claims that empty set symbol used by logicians for empty set is
    used by linguists with exactly the same meaning.

    The glyph ! is use by mathematicians to indicate "factorial", by
    phoneticists to indicate an aleveolar or postalveolar click, and by
    programmers in c and some other programming languages to indicate "not".

    Such overloading of symbols between disciplines (and even within
    disciplines) is common.

    > But capital "slashed o" (U+00D8) is not mentioned... And that letter
    > would be entirely appropriate for this purpose **in the contexts** where
    > it would stand for a "null consonant" (or empty string) in linguistics.

    It is not clear to me why the empty set symbol, which at least as the
    idea of emptiness associated with it, should be more inappropiate for
    use in linguistics for null character(s) than capital O-slash (Ø) which
      is a consonant in a real language and as such as no suggestion of
    emptiness about it, especially not to linguists who recognize its
    lowercase form as part of IPA.

    Also, linguists might be dealing with Norwegian and may wish to use
    actual Norwegian spelling in their explanations.

    > But capital "slashed o" (U+00D8) is not mentioned... And that letter
    > would be entirely appropriate for this purpose **in the contexts** where
    > it would stand for a "null consonant" (or empty string) in linguistics.

    Almost *any* character not otherwise used could be appropriate **in the

    > It does not appear to have wandered
    > into linguistics in any way (except by occasional typographic mistake,
    > and that does not count), even though there is use of a similar-looking
    > symbol.

    Can this supposition be documented?

    I thought the opposite, that the slashed zero form that sometimes
    appears in linguistics was a variant mathematical null set symbol, that
    the evolution was the opposite to what you suggest.

    > I think it would be less problematic to use the letter Ø for the empty
    > set (in a math context), than to use the EMPTY SET symbol (Ø) for any
    > linguistic entity in a word-like linguistic context.

    But it *is* being so used and has been used for quite some time. The
    word "problematic" is puzzling. What problems does this usage cause?

     From the web page by
    Markus Kuhn on the empty set symbol:

    > # Used in technical drawings and on product descriptions. Note that
    > # DIAMETER SIGN is an exact circle while EMPTY SET is often a digit zero,
    > # both with a stroke.

    Markus Kuhn distinguishes the diameter symbol from the empty set symbol
    but considers slashed zero as just a variant of the empty set sign,
    presumably from the same kind of glyph variation I have also seen in
    practise and which Ken Whistler commented on.

    The web page provides official
    Braille translations for IPA type symbols, including a braille symbol to
    be used for either the slashed zero or round slashed circle glyphs with
    the notation:

    > slashed zero, null or empty set

    Personally I prefer the slashed zero for null character(s) in linguistic

    I don't know if it also occurs in mathematical contexts as a null set

    Whether in linguistics the slashed zero should be considered a glyph
    variant of the mathematical empty set sign or whether the slashed zerio
    is a symbol unto itself (distinct from both the empty set sign and
    normal zero) is something for practising linguists to argue over or
    agree on.

    That the slashed zero glyph (used for null character(s) in linguistic
    texts) is to be distinguished from normal zero in linguistic texts is
    easy enough to demonstrate.

    Are there also linguistic texts that distinguish slashed zero from the
    mathematical empty set sign, giving different meanings to each?

    If so, then someone who wishes for Unicode to include slashed zero as an
    independant character should make a formal proposal to Unicode with
    sources to back up the difference in use.

    Even if linguists in general feel that the empty set form which often
    appears for (null character(s)) is a kludge for the proper slashed zero
    empty character symbol, a reasonable proposal could be presented, backed
    by one or more linguistic organizations.

    At least slashed zero might be made available as a variant of the round
    empty set symbol through a variation selector ... if it is *asked for*.

    But that is for those who use such notation regularly to decide.

    But I doubt you will find any linguist who would consider the Norwegian
    capital slashed O as anything other than a kludge replacement for
    either the standard round empty set symbol or the slashed zero symbol.

    Jim Allan

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