Precise definitions, not marketing copy — and where each term actually matters in real formatting decisions.
Compiled by Ata Rafi, Founder and Chief Formatter at Format Fix, from terms that come up in real formatting work, not general reference material.
Get A Free QuoteRTL describes a single language's reading direction. Bidi describes what happens when RTL and LTR text appear together in the same line or document.
The reading and layout direction for Arabic, Urdu, Hebrew, and Farsi — text, margins, and page progression all run right to left instead of left to right.
Text containing both right-to-left and left-to-right elements in the same line or paragraph — an English name embedded in an Arabic sentence, for example. Governed by the Unicode Bidirectional Algorithm.
See Arabic Text Direction in InDesign for how RTL and bidi text actually behave during layout.
Tashkeel is the broader category covering every diacritical mark. Harakat refers specifically to the short-vowel marks within that category.
The full category of diacritical marks placed above or below Arabic letters — harakat, shadda, sukoon, and tanween are all types of tashkeel.
Specifically the short-vowel marks — fatha, damma, and kasra — a subset of tashkeel, not a separate category from it.
See Why Tashkeel Placement Errors Change the Meaning of Your Text for why precise placement matters, and Quranic Text Formatting for Tajweed-specific recitation-rule terms like Madd and Ghunnah.
Tatweel is the elongation character itself. Kashida is the justification technique that stretches letterforms using tatweel to fill a line — the character and the technique are often blended into one definition, but they're distinct.
The elongation character (ـ) inserted between connected letters to stretch a word visually. On its own, it's just a character.
The justification technique that uses tatweel to stretch letterforms and fill a line, instead of adding space between words the way Latin-script justification does.
See What Affects Arabic Book Typesetting Cost for why kashida justification is a real cost factor, and Arabic Punctuation Placement Problems for a documented bug where kashida justification drops punctuation.
Naskh is the standard script for Arabic body text. Nastaliq is the standard script for Urdu and Persian, with a distinct sloping baseline that requires different typesetting handling.
The standard, upright script style used for most Arabic body text — the closest equivalent to a Latin serif text font.
The flowing, diagonally-sloped script style standard for Urdu and Persian, requiring different line-spacing and layout handling than Naskh.
See Arabic Font Selection & Licensing for how this choice affects font selection and licensing.
All three are calligraphic script styles used for decorative or ceremonial purposes rather than running body text — each with its own distinct form and typical use.
An ornate, densely interwoven script historically used for Ottoman court documents, now used decoratively for titles and covers.
A large, curved calligraphic script traditionally used for Quranic inscriptions, architectural text, and formal titles.
An angular, geometric script style, one of the oldest Arabic calligraphic forms, often used for logos and decorative headings.
See Arabic Calligraphy for Book Covers for how these styles are actually used in cover design.
A single glyph formed when two or more letters combine into one connected shape — lam-alif is the most common example, where the letters ل and ا merge into a distinct joined form.
See the portfolio for examples of how correct letter-joining and ligature handling looks in a finished manuscript.
Looking up an unfamiliar term encountered in a formatting quote, a font spec sheet, or another site's guide.
Cross-checking terminology while reviewing a formatted manuscript or vendor communication.
Needing a precise, correctly differentiated definition rather than marketing copy or an oversimplified summary.
Tashkeel is the full category of Arabic diacritical marks. Harakat refers specifically to the short-vowel marks — fatha, damma, and kasra — which are a subset of tashkeel, not a separate category.
Tatweel is the elongation character itself. Kashida is the line-justification technique that uses tatweel to stretch letterforms and fill a line.
RTL describes a single language's right-to-left reading direction. Bidi (bidirectional) text describes right-to-left and left-to-right elements appearing together in the same line or document.
Naskh is the standard, upright script used for most Arabic body text. Nastaliq is the flowing, diagonally-sloped script standard for Urdu and Persian, requiring different layout handling.
They're all calligraphic styles used decoratively rather than for body text, but each is visually distinct — Diwani is densely interwoven, Thuluth is large and curved, and Kufi is angular and geometric.
A ligature is a single glyph formed when two or more letters combine into one connected shape, built into the font itself — distinct from kashida or tatweel, which affect spacing, not letter shape.
