Numbers:
The standard behavior for the lowercase characters i j: additional accents above the character should replace the dot. See Unicode Core Specification, Chapter 7, section 7.1 Latin, Diacritics on i and j
As this is the standard behavior across Latin scripts, it should be considered the rule even where not explicitly flagged. It is flagged in this database only on notable character combinations to draw attention.
Proportional lining figures for numeric characters 0123456789 are required. Old-style figures (etc) are not acceptable variations; number spacing should match letter spacing and surrounding text.
Apostrophe and single-right-quote-like characters should have a curly, ball-and-tail like shape, rather than a straight or angled pipe shape. U+02BC Modifier Letter Apostrophe and most combining comma characters typically demonstrate the desired shape.
Local ogonek and glottal mark variant forms for some Haudenosaunee (Iroqouian) languages. Glottal mark and ogonek take the form of wedges that oppose each other in 180-degree rotation.
Ogonek wedge should be centered below the base letter. The top line of the glottal mark and bottom line of the ogonek need not be precisely aligned to the baselines; they are ideally tilted slightly further, so that the glottal mark wedge points even more upward and the ogonek wedge points even more downward.
Adjust Greek letter forms to a more Latin-like style for Latin-based writing systems that mix Latin and Greek characters, for example transcription systems or writing systems that adopt phonetic symbols. Narrower and more angular forms are preferred over circular and curled lines.
Examples include a narrower shape for θ theta characters (modeled on e.g. Times New Roman), or a serif form for λ lambda without the curled line.
Lower the middle of a vertically-centered character (e.g. mid dot) below the true center, on par with the horizontal line through A or e.
The diacritic mark U+0331 ◌̱ COMBINING MACRON BELOW should have a slightly longer length than usual, spanning the width of the base character that it positions beneath. This may improve visibility and suit the design of certain fonts, in particular sans-serif fonts.
Adjust the placement of U+0313 ◌̓ COMBINING COMMA ABOVE to be more space-efficient and readable above lowercase letters. Rather than appear directly above the tallest ascender in letters like k b ƛ (as per the Unicode Standard's general glyph representation), the combining mark should be lowered and adjusted closer to the visual center of the glyph, for example "nested" in the open space between the arms of letter k. This often has the benefit of avoiding clipping.
The ogonek hook should be horizontally centered below the base character, in contrast to standard forms like ą Ę where the hook may connect at the corner.
Give superscript letters (such as ⁿ) the same height and treatment as modifier letters (such as ʰ). They should be optimized for use in text rather than equations.
OpenType Layout implementation of variations:
X001X003X002X004X005X006X007X008OpenType Layout implementation of variations:
X001X003X002X004X005X006X007X008