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Diacritical markings.

Unicode allows adding diacritical markings to ordinary characters, primarily to support the letters of many languages. In most cases these indicate details of pronunciation, but mathematicians sometimes find it convenient to employ the markings for entirely different purposes. Unicode has a code range (0300-036F) of various diacritical marks that combine with other characters. Many of them are shown here, with a few markings from other code ranges. They are not intended to be an orthogonal set.

Unfortunately, many implementations do not yet support these well. In most cases, a marking should be centered over or under the primary character's glyph, but sometimes it appears elsewhere, or is missing entirely. Sometimes the extra marking overlaps the main character when it ought to be completely separate.

In the examples below, the "Y" (&#x59;), "y" (&#x79;), and "o" (&#x6F;) characters are ordinary letters from page zero of Unicode, as inherited from long-established ASCII. The "o" is included merely to to give the diacriticized "Y" and "y" a typographical context for better understanding. Surrounding all that in the source code are the <tt> and </tt> markup symbols of HTML, in order to effect a monospace font. On the author's computer, this gave better results than a variable-pitch font.

In Unicode documentation, it is customary to use a dotted circle ◌ (&#x25CC;) as a foundation when giving examples of combining marks. However, this circle does not have a descender, and it may not rise to the full height of an ascender. The characters "Y" and "y" were chosen because they do satisfy these needs.

Authors should remember that some Unicode characters have diacritical marks "built in"; The choice between combinings and built-ins requires consideration of the context. Example:

All the official Unicode names of combining characters in the tables below begin with the word "combining", so it is here abbreviated as "c.".

In table D-1, each row has markings in above-below pairs:

Table D-2 has some above markings:

Table D-3 has some below markings, with related markings in the same row:

Table D-4 has some overlay markings:

If the markings of table D-5 are properly implemented, the lines will connect from one character to the next, and be centered on the whole group:

Markings can be cascaded, with examples below. However, the risk of incorrect rendering increases with the number of markings.

Cascading to the point of abuse leads to Zalgo text.