∅ the empty set

Empty set symbol

Oddly enough, I'm having trouble finding a way to display a empty set symbol that works on Internet Explorer (7 included).

The symbol ∅ doesn't display correctly. It shows up as a square. Converting it to its HTML entity ∅ or its hex equivalent ∅ doesn't solve the problem.

So, I set out to discover how maths websites display this symbol, and apparently most of them use inline images (sigh).

• http://en.wikipedia.org/wiki/Empty_set
• http://mathworld.wolfram.com/EmptySet.html
• http://planetmath.org/encyclopedia/EmptySet.html

or the alternate notation {}.

• http://mathforum.org/library/drmath/view/52387.html
• http://en.wikipedia.org/wiki/Empty_set

The few website that actually display the actual symbol use the Danish and Norwegian letter capital o slash [Ø] that translates into Ø. Although it is semantically different from the empty the symbol per se, and depending on the font used it is not circular but oval shaped, it does the trick. All browsers I've tested render it correctly.

Time to get pragmatic, and launched that search & replace.

Technorati Tags: html, ie, symbol, ∅

Ø permalink: http://www.davidroessli.com/logs/2006/12/empty_set_symbol/