Editing Diameter (section)

== Symbol ==
{{redirect|⌀}}
[[Image:Technical Drawing Hole 01.svg|thumb|upright 0.5|Sign ⌀ in a technical drawing]]
[[File:Hama UV Filter 1.jpg|thumb|A [[photographic filter]] marked as having a 58mm thread diameter]]
The [[symbol]] or [[Variable (mathematics)|variable]] for diameter, {{char|⌀}}, is sometimes used in technical drawings or specifications as a prefix or suffix for a number (e.g. "⌀ 55 mm"), indicating that it represents diameter.<ref>{{cite book|title=Interpretation of Geometric Dimensioning and Tolerancing|first=Daniel E.|last=Puncochar|publisher=Industrial Press Inc.|year=1997|isbn=9780831130725|page=5|url=https://books.google.com/books?id=76la9qNmt24C&pg=PA5}}</ref> Photographic [[filter thread]] sizes are often denoted in this way.<ref>{{cite book|title=Introduction to Digital Photography|first=Joseph|last=Ciaglia|publisher=Prentice Hall|year=2002|isbn=9780130321367|page=9|quote=The filter diameter (in mm) usually follows the symbol ⌀}}</ref>

The symbol has a [[code point]] in [[Unicode]] at {{unichar|2300|Diameter sign|html=}}, in the [[Miscellaneous Technical]] set. It should not be confused with several other characters (such as {{unichar|00D8|nlink=}} or {{unichar|2205|nlink=Null sign}}) that resemble it but have unrelated meanings.<ref>{{cite book|title=Unicode Explained|first=Jukka K.|last=Korpela|publisher=O'Reilly Media, Inc.|year=2006|isbn=9780596101213|page=171|url=https://books.google.com/books?id=lxndiWaFMvMC&pg=PA171}}</ref> It has the [[compose sequence]] {{key press|[[Compose key|Compose]]|d|i|chain=}}.<ref>{{cite web |url=http://cgit.freedesktop.org/xorg/lib/libX11/plain/nls/en_US.UTF-8/Compose.pre |title=UTF-8 (Unicode) compose sequence |last=Monniaux |first=David |access-date=2018-07-13}}</ref>