Case in an Arabic number phrase is not one ending attached to “the number.” It is distributed across the components. Eleven and 13–19 are compound forms built on fatḥ and do not display the surrounding case; twelve changes its first component; the decades change ـون to ـين; and both parts of 21–99 participate in the phrase's case. Large-number words such as مئة، ألف، مليون behave as noun-like heads.
English gives learners no direct model because twelve, twenty, and million never change after a preposition or as an object. The reliable method is to identify the numeral range, determine the syntactic role of the complete phrase, and then mark only the component or components that can inflect.
The structure of noun-like large-number heads is developed on Hundreds, Thousands, Millions, and Billions; this page concentrates on where case is pronounced.
Case and the counted noun are separate questions
Two rules operate at once:
- The numeral expression receives nominative, accusative, or genitive case from its role in the sentence.
- The counted noun takes the form required by that numeral range.
For 11–99, the counted noun remains singular accusative even when the whole number phrase follows a preposition. For exact hundreds and thousands, the counted noun is singular genitive. This is why the last noun does not necessarily display the same case as the numeral.
تحدثت مع ثلاثة وعشرين طبيبا بعد المؤتمر.
taḥaddathtu maʿa thalāthatin wa-ʿishrīna ṭabīban baʿda l-muʾtamar.
I spoke with twenty-three doctors after the conference.
مع makes ثلاثةٍ وعشرين genitive, but طبيبًا is still the singular accusative specification required after 23.
Eleven and 13–19: case is not outwardly visible
أحد عشر and compounds from 13 through 19 are normally built on fatḥ in all three syntactic positions. Their gender patterns still matter, but nominative, accusative, and genitive do not produce different surface forms. The counted noun is singular accusative.
| Role | Example with 11 | Example with 13 |
|---|---|---|
| nominative | أحد عشر طالبا | ثلاثة عشر طالبا |
| accusative | أحد عشر طالبا | ثلاثة عشر طالبا |
| genitive | أحد عشر طالبا | ثلاثة عشر طالبا |
حضر أحد عشر عضوا جلسة الصباح.
ḥaḍara ʾaḥada ʿashara ʿuḍwan jalsata ṣ-ṣabāḥ.
Eleven members attended the morning session.
تحدث المدير مع ثلاثة عشر موظفا.
taḥaddatha l-mudīru maʿa thalāthata ʿashara muwaẓẓafā.
The director spoke with thirteen employees.
The second number is grammatically genitive after مع, yet ثلاثة عشر remains built on fatḥ. “No visible change” does not mean “no syntactic case”; it means this compound does not express the contrast morphologically.
Twelve: the first component inflects
Twelve is the essential exception. Its first part behaves like a construct dual: nominative اثنا/اثنتا, accusative or genitive اثني/اثنتي. The second part عشر/عشرة remains built on fatḥ. The counted noun is singular accusative.
| Case | Masculine noun | Feminine noun |
|---|---|---|
| nominative | اثنا عشر طالبا | اثنتا عشرة طالبة |
| accusative | اثني عشر طالبا | اثنتي عشرة طالبة |
| genitive | اثني عشر طالبا | اثنتي عشرة طالبة |
وصل اثنا عشر قطارا في الموعد.
waṣala thnā ʿashara qiṭāran fī l-mawʿid.
Twelve trains arrived on time.
راجعت اثني عشر طلبا قبل الظهر.
rājaʿtu thnay ʿashara ṭalaban qabla ẓ-ẓuhr.
I reviewed twelve applications before noon.
شاركت اثنتا عشرة جامعة في المشروع.
shārakati thnatā ʿashrata jāmiʿatan fī l-mashrūʿ.
Twelve universities participated in the project.
تعاونت المؤسسة مع اثنتي عشرة جامعة.
taʿāwanati l-muʾassasatu maʿa thnatay ʿashrata jāmiʿa(h).
The organization collaborated with twelve universities.
The initial alif of اثنا/اثنتا has hamzat al-waṣl. It receives a helping vowel at utterance beginning but elides in connected speech after وصل or مع; the romanizations therefore begin the connected numeral with thn-, not ʾithn-.
The decades: nominative ـون, oblique ـين
Twenty through ninety decline like sound masculine plurals. Use ـون in the nominative and ـين in the accusative and genitive. Gender does not change the decade form.
نجح خمسون طالبا في الاختبار.
najaḥa khamsūna ṭāliban fī l-ikhtibār.
Fifty students passed the exam.
كرمت المدرسة خمسين طالبة في الحفل.
karramati l-madrasatu khamsīna ṭālibatan fī l-ḥafl.
The school honored fifty female students at the ceremony.
تحدث التقرير عن خمسين حالة جديدة.
taḥaddatha t-taqrīru ʿan khamsīna ḥālatan jadīda(h).
The report discussed fifty new cases.
The last two both use خمسين, but for different reasons: direct-object accusative and prepositional genitive. Their counted nouns remain singular accusative.
Coordinated numerals: both parts share the case
In 21–99, the unit and decade are linked by و but remain coordinated case-bearing elements. The decade shows nominative ـون versus oblique ـين. Units one and three through nine also take the appropriate short case ending; two has the visible dual contrast اثنان/اثنين or اثنتان/اثنتين.
| Case | 23 with a masculine noun | 32 with a feminine noun |
|---|---|---|
| nominative | ثلاثة وعشرون باحثا | اثنتان وثلاثون باحثة |
| accusative | ثلاثة وعشرين باحثا | اثنتين وثلاثين باحثة |
| genitive | ثلاثة وعشرين باحثا | اثنتين وثلاثين باحثة |
شارك ثلاثة وعشرون باحثا في الدراسة.
shāraka thalāthatun wa-ʿishrūna bāḥithan fī d-dirāsa(h).
Twenty-three researchers participated in the study.
قابلت اثنتين وثلاثين باحثة خلال المؤتمر.
qābaltu thnatayni wa-thalāthīna bāḥithatan khilāla l-muʾtamar.
I met thirty-two female researchers during the conference.
Large-number heads carry ordinary noun case
مئة، ألف، مليون، مليار receive case according to their role, while the noun they directly govern is genitive. Dual large-number heads show the familiar nominative ـا versus oblique ـي, and lose ن before a direct complement.
بلغت المبيعات مليون دولار هذا الشهر.
balaghati l-mabīʿātu milyūna dūlārin hādhā sh-shahr.
Sales reached one million dollars this month.
ارتفع العدد إلى مليوني مستخدم.
ʾirtafaʿa l-ʿadadu ʾilā milyūnay mustakhdim.
The total rose to two million users.
The first مليونَ is accusative after بلغت “reached.” The second مليوني is genitive after إلى and construct before مستخدم. Formal writing represents these relationships even when natural pausal delivery suppresses a final short vowel.
Case in digits is heard, not seen
Digits do not display Arabic case endings, but the words used to read them still inflect. In a grammar-focused reading, ٥٢ as a subject is اثنان وخمسون, while as an object it is اثنين وخمسين.
وافقت ٥٢ دولة على البيان.
wāfaqati thnatāni wa-khamsūna dawlatan ʿalā l-bayān.
Fifty-two countries approved the statement.
Here feminine دولة selects feminine agreeing اثنتان, and the subject role selects nominative اثنتان وخمسون. The written digits do not reverse simply because the surrounding script runs right to left.
Common Mistakes
Missing the case change in twelve
❌ قابلت اثنا عشر موظفا.
Incorrect — twelve is a direct object, so its first component must be oblique اثني.
✅ قابلت اثني عشر موظفا.
qābaltu thnay ʿashara muwaẓẓafā.
I met twelve employees.
Leaving a decade nominative after a preposition
❌ تحدثت مع أربعون مشاركا.
Incorrect — after مع, the decade must be genitive أربعين.
✅ تحدثت مع أربعين مشاركا.
taḥaddathtu maʿa ʾarbaʿīna mushārikā.
I spoke with forty participants.
Making the counted noun plural after 11–99
❌ راجعت خمسة عشر طلبات.
Incorrect — the counted noun after 15 is singular accusative.
✅ راجعت خمسة عشر طلبا.
rājaʿtu khamsata ʿashara ṭalabā.
I reviewed fifteen applications.
Applying one gender pattern to every range
❌ شاركت ثلاث عشرة طالبا.
Incorrect — with masculine طالب, the unit in 13 takes the polarity form ثلاثة.
✅ شارك ثلاثة عشر طالبا.
shāraka thalāthata ʿashara ṭālibā.
Thirteen students participated.
Reversing digits in right-to-left text
❌ الرقم ٥٢ يعني خمسة وعشرين.
Incorrect — ٥٢ is 52, not 25.
✅ الرقم ٥٢ يعني اثنين وخمسين.
ar-raqmu thnāni wa-khamsūna yaʿnī thnayni wa-khamsīn.
The number 52 means fifty-two.
Key Takeaways
- Eleven and 13–19 are built on fatḥ; their syntactic case is real but not outwardly contrasted.
- In twelve, only the first component visibly changes: اثنا/اثنتا nominative and اثني/اثنتي oblique.
- Decades use ـون in the nominative and ـين in the accusative or genitive.
- In 21–99, both coordinated components share the phrase's case, while the counted noun stays singular accusative.
- Large-number heads take ordinary noun case and directly govern a genitive complement.
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Start learning Arabic →Related Topics
- Hundreds, Thousands, Millions, and BillionsA2 — Build large Arabic numbers by treating hundred, thousand, million, and billion as noun-like heads with governed complements.
- Numbers 3–10 and Gender PolarityA2 — Build 3–10 phrases by choosing the numeral opposite the singular noun’s gender, then using a plural genitive counted noun.
- Numbers 0–10 in IsolationA1 — Read, pronounce, and distinguish the citation and gender-paired forms of Arabic zero through ten before building counted-noun phrases.