Arabic expresses a fraction through an ordinary noun such as نصف “half,” ثلث “third,” or ربع “quarter.” That noun can take case, form a dual, become plural, and govern a following genitive: ثلثُ السكان “one third of the population,” ثلثا السكان “two thirds,” and ثلاثةُ أرباعِ السكان “three quarters.” This noun-like structure is very different from English slash notation, but it makes the grammar predictable.
Ratios and percentages add several conventional frames: من “out of/from,” إلى “to,” and بالمئة / في المئة “percent.” The number inside each frame still has its own gender and case behavior. The referent after من does not retroactively change the form of an already complete percentage.
The basic fraction nouns
The traditional lexical fractions from one half through one tenth are mostly short nouns. Their vowels are not safely recoverable from unvocalized spelling, so learn their spoken forms explicitly.
| Value | Arabic | Romanization |
|---|---|---|
| 1/2 | نصف | niṣf |
| 1/3 | ثلث | thuluth |
| 1/4 | ربع | rubʿ |
| 1/5 | خمس | khumus |
| 1/6 | سدس | sudus |
| 1/7 | سبع | subuʿ |
| 1/8 | ثمن | thumun |
| 1/9 | تسع | tusuʿ |
| 1/10 | عشر | ʿushr |
The fraction noun is the head of an iḍāfa. It takes the case required by the sentence; the denominator—the whole being divided—follows in the genitive.
يشغل المخزن ثلث مساحة المبنى.
yashghalu l-makhzanu thulutha misāḥati l-mabnā.
The storeroom occupies one third of the building’s floor area.
تحدث التقرير عن ربع سكان المنطقة.
taḥaddatha t-taqrīru ʿan rubʿi sukkāni l-minṭaqa(h).
The report discussed one quarter of the region’s population.
In the first sentence, ثلثَ is the direct object and therefore accusative. In the second, ربعِ is genitive after عن. English one third of does not show either relation overtly.
Two parts: use the dual fraction
For two thirds, two fifths, and similar fractions, Arabic can put the fraction noun in the dual. A construct dual loses its final ن: nominative ثلثا الميزانية, accusative/genitive ثلثي الميزانية.
غطى الدعم ثلثي تكلفة المشروع.
ghaṭṭā d-daʿmu thuluthayi taklifati l-mashrūʿ.
The grant covered two thirds of the project’s cost.
ثلثا المشاركين من النساء.
thuluthā l-mushārikīna mina n-nisāʾ.
Two thirds of the participants are women.
The direct object ثلثي is oblique, whereas the subject ثلثا is nominative. This visible ـا / ـي contrast belongs to the dual fraction noun, not to the following genitive.
Numerators from three onward
When the numerator is three or more, count plural fraction nouns by the ordinary cardinal rules. Since ربع “quarter” is masculine, three quarters uses polarity-marked ثلاثة, followed by plural genitive أرباع.
صوت ثلاثة أرباع الأعضاء لصالح الاقتراح.
ṣawwata thalāthatu ʾarbāʿi l-ʾaʿḍāʾi li-ṣāliḥi l-iqtirāḥ.
Three quarters of the members voted for the proposal.
يمثل الكسر ٥⁄٨ خمسة أثمان الكمية.
yumaththilu l-kasru khamsa ʿalā thamāniya khamsata ʾathmāni l-kammiyya(h).
The fraction 5/8 represents five eighths of the quantity.
In خمسة أثمان, masculine singular ثمن selects خمسة, and the plural أثمان is genitive. The numeral in the example is accusative because the complete fraction phrase is the object of يمثل. Slash notation ٥⁄٨ preserves numerator-over-denominator order even inside a right-to-left line.
Ratios with إلى and rates with من
A ratio is commonly introduced by نسبة and joins its two values with إلى. The prepositions control case where a form visibly declines.
خلط الفني المحلولين بنسبة ثلاثة إلى اثنين.
khalaṭa l-fanniyyu l-maḥlūlayni bi-nisbati thalāthatin ʾilā thnayn.
The technician mixed the two solutions in a ratio of three to two.
ثلاثةٍ is genitive as the complement of نسبة, and اثنين is genitive after إلى. In technical tables, the same ratio may appear as ٣:٢. Read the values in their stated order; bidirectional layout does not turn 3:2 into 2:3.
The frame واحد من كل خمسة means “one out of every five.” The first numeral refers to the selected member; the numeral after كل counts the comparison group.
أفاد المسح بأن واحدا من كل خمسة موظفين يعمل عن بعد.
ʾafāda l-masḥu bi-ʾanna wāḥidan min kulli khamsati muwaẓẓafīna yaʿmalu ʿan buʿd.
The survey reported that one in every five employees works remotely.
وجدت الدراسة أن واحدة من كل خمس شركات غيرت سياستها.
wajadati d-dirāsatu ʾanna wāḥidatan min kulli khamsi sharikātin ghayyarat siyāsatahā.
The study found that one in every five companies changed its policy.
The feminine واحدة refers to one company. خمس شركات has the 3–10 pattern: feminine شركة selects خمس, and شركات is plural genitive. The masculine employee example instead uses خمسة موظفين.
Percent: بالمئة, في المئة, and the symbol ٪
بالمئة and في المئة both mean “percent” (formal and general). في المائة is the traditional spelling with internal alif; contemporary institutional writing also widely uses المئة. When a percentage is spelled out, the conventional numeral is understood against masculine جزء “part”: خمسة وثمانون بالمئة. A following population is normally introduced with من and does not control that numeral’s gender.
بلغت نسبة الحضور ٨٥ بالمئة في الجلسة الأولى.
balaghat nisbatu l-ḥuḍūri khamsatan wa-thamānīna bi-l-miʾati fī l-jalsati l-ʾūlā.
Attendance reached 85 percent in the first session.
مثلت الطالبات ٤٢ بالمئة من المشاركين في البرنامج.
maththalati ṭ-ṭālibātu thnayni wa-ʾarbaʿīna bi-l-miʾati mina l-mushārikīna fī l-barnāmaj.
Female students made up 42 percent of the participants in the program.
The noun after من is genitive: من المشاركين. It does not control the unit digit of ٤٢. The percentage is already a numerical rate, conventionally understood as parts per hundred.
A percentage and a percentage-point change are not the same. If a rate rises from 40% to 45%, it rises by five percentage points but by 12.5 percent relative to its old value. Arabic makes the first meaning explicit with نقطة مئوية.
ارتفع معدل المشاركة خمس نقاط مئوية هذا العام.
ʾirtafaʿa muʿaddalu l-mushārakati khamsa niqāṭin miʾawiyyatin hādhā l-ʿām.
The participation rate rose by five percentage points this year.
نقطة is feminine, so five is خمس, and its plural نقاط is genitive. The nonhuman plural adjective appears as feminine singular مئوية.
أضاف التعديل إحدى عشرة نقطة مئوية إلى نسبة التغطية.
ʾaḍāfa t-taʿdīlu ʾiḥdā ʿashrata nuqṭatan miʾawiyyatan ʾilā nisbati t-taghṭiya(h).
The amendment added eleven percentage points to the coverage rate.
Eleven takes singular accusative نقطةً, not a plural. The feminine unit digit إحدى agrees with feminine نقطة, while the second element عشرة has the corresponding feminine-counted form.
A decimal percentage
Formal reports use either Arabic decimal separator ٫ or, depending on house style and software, an international decimal point. A common word-for-symbol reading uses فاصلة “decimal point/comma,” then reads the digits to its right.
سجل التضخم ٢٫٥ بالمئة في الربع الأخير.
sajjala t-taḍakhkhumu thnayni fāṣila khamsa(h) bi-l-miʾati fī r-rubʿi l-ʾakhīr.
Inflation registered 2.5 percent in the final quarter.
Here ٢٫٥ is read as اثنان فاصلة خمسة when cited as a decimal value; in the accusative environment after سجل, careful fully inflected reading can mark the integer part as اثنين, while the digits after the separator are commonly read as labels. Exact decimal place value, separator choice, and prices receive a full treatment on Decimals, Prices, and Currencies.
Common Mistakes
Using the feminine-counted form with a masculine fraction noun
❌ وافق ثلاث أرباع الأعضاء.
Incorrect — ربع is masculine, so three quarters begins with ثلاثة.
✅ وافق ثلاثة أرباع أعضاء اللجنة.
wāfaqa thalāthatu ʾarbāʿi ʾaʿḍāʾi l-lajna(h).
Three quarters of the committee members agreed.
Keeping a plural counted noun after twelve
❌ الزيادة اثنتا عشرة نقاط مئوية.
Incorrect — twelve takes a singular accusative counted noun.
✅ الزيادة اثنتا عشرة نقطة مئوية.
ʾaz-ziyādatu thnatā ʿashrata nuqṭatan miʾawiyya(h).
The increase is twelve percentage points.
Missing oblique case on twelve after a preposition
❌ ارتفع المؤشر باثنتا عشرة نقطة.
Incorrect — after بـ, the first element of twelve must be oblique اثنتي.
✅ ارتفع المؤشر باثنتي عشرة نقطة مئوية.
ʾirtafaʿa l-muʾashshiru bi-thnatay ʿashrata nuqṭatan miʾawiyya(h).
The index rose by twelve percentage points.
Leaving a decade nominative after a transitive verb
❌ أظهر الاستطلاع أن نسبة التأييد بلغت ثلاثون بالمئة.
Incorrect in fully inflected MSA — the measured result after بلغت is accusative, so use ثلاثين.
✅ أظهر الاستطلاع أن نسبة التأييد بلغت ثلاثين بالمئة.
ʾaẓhara l-istiṭlāʿu ʾanna nisbata t-taʾyīdi balaghat thalāthīna bi-l-miʾa(h).
The survey showed that support reached 30 percent.
Reversing the values in an RTL ratio
❌ النسبة ٣:٢ تعني اثنين إلى ثلاثة.
Incorrect — the written ratio is three to two; RTL context does not reverse its values.
✅ النسبة ٣:٢ تعني ثلاثة إلى اثنين.
ʾan-nisbatu thalātha ʾilā thnayn taʿnī thalāthatan ʾilā thnayn.
The ratio 3:2 means three to two.
Key Takeaways
- A lexical fraction is a case-bearing noun that governs the whole being divided in the genitive.
- Use a construct dual for two parts: nominative ثلثا, accusative/genitive ثلثي.
- From three onward, the numerator counts a plural fraction noun: masculine ربع gives ثلاثة أرباع.
- Ratios use frames such as نسبة ثلاثة إلى اثنين; “one in five” uses واحد من كل خمسة with the proper gender of the selected and counted nouns.
- بالمئة / في المئة expresses percent, while نقطة مئوية expresses a percentage-point change. The latter is an ordinary counted-noun phrase and follows all range rules.
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