Abstract Character (Unicode)
Last updated at 1:39 pm UTC on 15 December 2015
From The Unicode Standard
p. 65 of http://www.unicode.org/versions/Unicode8.0.0/UnicodeStandard-8.0.pdf
The figure illustrates the relationship between abstract characters and code points, which
together constitute encoded characters.
Note that some abstract characters may be associated with multiple, separately encoded characters (that is, be encoded “twice”).
In other instances, an abstract character may be represented by a sequence of two (or more) other
encoded characters. The solid arrows connect encoded characters with the abstract characters that they represent and encode
Extract from UnicodeData.txt (the Unicode Character Database)
0041;LATIN CAPITAL LETTER A;Lu;0;L;;;;;N;;;;0061;
00C5;LATIN CAPITAL LETTER A WITH RING ABOVE;Lu;0;L;0041 030A;;;;N;LATIN CAPITAL LETTER A RING;;;00E5;
030A;COMBINING RING ABOVE;Mn;230;NSM;;;;;N;NON-SPACING RING ABOVE;;;;
212B;ANGSTROM SIGN;Lu;0;L;00C5;;;;N;ANGSTROM UNIT;;;00E5;
Some abstract characters may be encoded by different code points. U+03A9 greek capital letter omega and U+2126 ohm sign both correspond to the same abstract character ‘Ω’, and must be treated identically. [Source]