Microsoft Typography | Developer information | Specifications | OpenType font development
Arabic OpenType Specification | Terms | Shaping | Features | Other | Appendix


Terms

The following terms are useful for understanding the layout features and script rules discussed in this document.

Base Glyph - Any glyph that can have a diacritic mark above or below it. Layout operations are defined in terms of a base glyph, not a base character, as a ligature may act as the base.

Character - Each character represents a Unicode character code point. For example, the 'lam' character is (U+0644). A character may have multiple forms of glyphs.

Diacritic Mark - A character that is positioned above or below a character to provide pronunciation guidance.

Glyph - A glyph represents a form of one or more characters. For example, the final, initial and medial 'lam' glyphs (U+FEDE, U+FEDF & U+FEEO) are all forms of the 'lam' character (U+0644).

Kashida - Also known as the 'tatweel' character (U+0640). This character is used for elongation between connecting characters and is used for justification.

Ligature - A combination of glyphs that join to form a single glyph. For example, the 'lam alef' combinations of glyphs are mandatory ligatures for Arabic. Other ligatures, like 'lam meem initial', are optional.



this page was last updated 25 February 2002
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Arabic OpenType Specification | Terms | Shaping | Features | Other | Appendix
Microsoft Typography | Developer information | Specifications | OpenType font development