science

Kashida

Kashida is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Kashida rather than just read about it. In short: Kashida or kasheeda (Persian: کَشِیدَه, romanized: kašīda, lit. 'extended' or 'stretched' or 'lengthened'), also known as tatweel or tatwīl (Arabic: تَطْوِيل, romanized: taṭwīl), is a type of justification in written Arabic scripts, in which the line connecting letters is extended. In contrast to white-space justification, which increases the length of a line of text by expanding spaces between words or individual l…

Key takeaways

Kashida belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Kashida to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Kashida from memory before moving on to harder problems.

Reference excerpt

Kashida or kasheeda (Persian: کَشِیدَه, romanized: kašīda, lit. 'extended' or 'stretched' or 'lengthened'), also known as tatweel or tatwīl (Arabic: تَطْوِيل, romanized: taṭwīl), is a type of justification in written Arabic scripts, in which the line connecting letters is extended. In contrast to white-space justification, which increases the length of a line of text by expanding spaces between words or individual letters, kasheeda creates justification by elongating characters at certain points. Kasheeda justification can be combined with white-space justification. The analog in European (Latin-based) typography (expanding or contracting letters to improve spacing) is sometimes called expansion, and falls within microtypography. Kashida is considerably easier and more flexible, however, because Arabic–Persian scripts feature prominent horizontal strokes, whose lengths are accordingly flexible. For example, al-ḥamdu and Raḥīm with and without kasheeda may look like the following:

The terms kasheeda and tatweel can also refer to a character that represents this elongation (ـ) or to one of a set of glyphs of varying lengths that implement this elongation in a font. The Unicode standard assigns code point U+0640 ـ ARABIC TATWEEL.

The kasheeda can take a subtle downward curvature in some calligraphic styles and handwriting. However, the curvilinear stroke is not feasible for most basic fonts, which merely use a completely flat underscore-like (or string-like) stroke for kashida. In addition to letter spacing and justification, calligraphers also use kasheeda for emphasis and as book or chapter titles. In modern Arabic mathematical notation, kasheeda appears in some operation symbols that must stretch to accommodate associated contents above or below. Kasheeda generally only appears in one word per line, and one letter per word. Furthermore, experts recommend kasheeda only between certain combinations of letters (typically those that cannot form a ligature). Some calligraphers who were paid by the page used a large number of kasheeda in order to stretch content over more pages. The branding of the 2022 FIFA World Cup in Qatar applies kasheeda to Latin script, connecting the bottom of the "t" and the second "a" in the host country's name. A similar concept exists in Hebrew, where certain letters (אדהכלםרת←ﬡﬢﬣﬤﬥﬦﬧﬨ) may be stretched or elongated horizontally for the purpose of block justification in text. This is commonly used in Ktav Stam.

Worked examples

Example 1 — a first encounter with Kashida

Start with the simplest possible case. Write down what Kashida claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Kashida before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Kashida ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Kashida

In research: Kashida appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Kashida in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Kashida is common in secondary-school and first-year university syllabi. It links to neighbouring topics Arabic language stubs, Arabic punctuation and symbols, Typography, so understanding it makes those chapters shorter.
In everyday life: Look for Kashida outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Kashida in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Kashida means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Kashida out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Kashida in simple terms?

Why does Kashida matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Kashida?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Kashida.