Cardinal numbers answer “how many?” Ordinals answer “which one in an ordered sequence?” That change in meaning reorganizes the grammar. In ثلاثة كتب “three books,” three precedes a plural genitive noun and shows gender polarity. In الكتاب الثالث “the third book,” the ordinal follows a singular noun and behaves like an adjective: it agrees in gender, definiteness, and case.
Formal Modern Standard Arabic uses this adjectival system in chapters, floors, rankings, dates, centuries, and official labels. Spoken dialects often pronounce or build some forms differently (regional); the patterns here are those of careful contemporary MSA (formal).
Calendar applications are developed separately on Dates, Years, and Centuries.
Ordinals are agreeing adjectives
Ordinals from third through tenth are based on the active-participle pattern فاعل. Unlike cardinal 3–10, they show ordinary agreement rather than gender polarity.
| Rank | Masculine | Feminine |
|---|---|---|
| 1st | أول | أولى |
| 2nd | ثان | ثانية |
| 3rd | ثالث | ثالثة |
| 4th | رابع | رابعة |
| 5th | خامس | خامسة |
| 6th | سادس | سادسة |
| 7th | سابع | سابعة |
| 8th | ثامن | ثامنة |
| 9th | تاسع | تاسعة |
| 10th | عاشر | عاشرة |
بدأ الفصل الأول اليوم.
badaʾa l-faṣlu l-ʾawwalu l-yawm.
The first academic term began today.
قرأت الصفحة الأولى من التقرير.
qaraʾtu ṣ-ṣafḥata l-ʾūlā mina t-taqrīr.
I read the first page of the report.
ناقشنا الاقتراح الثالث في الاجتماع.
nāqashnā l-iqtirāḥa th-thālitha fī l-ijtimāʿ.
We discussed the third proposal at the meeting.
وافقت اللجنة على الخطة الثالثة.
wāfaqati l-lajnatu ʿalā l-khuṭṭati th-thālitha(h).
The committee approved the third plan.
In the last pair, masculine اقتراح selects الثالث, while feminine خطة selects الثالثة. The cardinal polarity forms would be ثلاثة اقتراحات but ثلاث خطط. Do not import that reversal into ordinals.
First and second are irregular
“First” uses the suppletive pair أول/أولى, not a predictable form derived from واحد/واحدة. “Second” uses ثانٍ in an indefinite nominative or genitive position, ثانيًا in the indefinite accusative, and الثاني when definite. Its feminine ثانية declines regularly.
وصل متسابق ثان بعد دقائق.
waṣala mutasābiqun thānin baʿda daqāʾiq.
A second contestant arrived minutes later.
كرمت المدرسة المتسابقة الثانية.
karramati l-madrasatu l-mutasābiqata th-thāniya(h).
The school honored the second female contestant.
The spelling ثان in the first example is not a typo. As an indefinite defective adjective in the nominative or genitive, final ي is deleted and compensated by tanwīn kasr. With الـ, in an iḍāfa, or in the accusative, the ي is present where the morphology requires it.
There is no useful logic that derives أول from “one.” Memorize الأول/الأولى and الثاني/الثانية as high-frequency pairs.
Definiteness identifies a rank in a known sequence
The ordinal normally matches its noun in definiteness. الفصل الثالث is “the third chapter”; فصل ثالث is “a third chapter” or “another, third chapter.” English marks the usual ordinal only once with the; Arabic marks both noun and adjective with الـ.
أضاف الكاتب فصلا ثالثا إلى الكتاب.
ʾaḍāfa l-kātibu faṣlan thālithan ʾilā l-kitāb.
The author added a third chapter to the book.
حذف المحرر الفصل الثالث لاحقا.
ḥadhafa l-muḥarriru l-faṣla th-thālitha lāḥiqā.
The editor later deleted the third chapter.
An ordinal can also stand without an overt noun when the class is understood. It then carries the gender of the omitted referent.
فازت ليلى بالجائزة الأولى، وحصلت مريم على الثانية.
fāzat laylā bi-l-jāʾizati l-ʾūlā, wa-ḥaṣalat maryamu ʿalā th-thāniya(h).
Layla won first prize, and Maryam received second.
الثانية remains feminine because the omitted noun is الجائزة.
Eleventh through nineteenth
Compound ordinals from 11th through 19th place the unit before a form of ten. Both parts agree with the noun's gender: الحادي عشر but الحادية عشرة; الثالث عشر but الثالثة عشرة. The two parts normally form a compound built on fatḥ, so surrounding nominative, accusative, and genitive roles do not create an audible case contrast within the ordinal.
| Rank | Masculine | Feminine |
|---|---|---|
| 11th | الحادي عشر | الحادية عشرة |
| 12th | الثاني عشر | الثانية عشرة |
| 13th | الثالث عشر | الثالثة عشرة |
| 19th | التاسع عشر | التاسعة عشرة |
يعرض الفصل الحادي عشر نتائج الدراسة.
yaʿriḍu l-faṣlu l-ḥādiya ʿashara natāʾija d-dirāsa(h).
The eleventh chapter presents the study's results.
وصلت البعثة الثانية عشرة إلى المخيم.
waṣalati l-baʿthatu th-thāniyata ʿashrata ʾilā l-mukhayyam.
The twelfth delegation arrived at the camp.
نشر المقال في العدد الخامس عشر.
nushira l-maqālu fī l-ʿadadi l-khāmisa ʿashar.
The article was published in the fifteenth issue.
The phrase في العدد is genitive, but the compound ordinal الخامس عشر remains built on fatḥ. This differs from cardinal twelve, whose first component changes between اثنا and اثني.
Twentieth through ninetieth
The ordinal decades have the same forms as the cardinal decades and decline like sound masculine plurals: العشرون in the nominative and العشرين in the accusative or genitive. They do not acquire a feminine ـة when modifying a feminine noun.
الطابق العشرون مخصص للمؤتمرات.
aṭ-ṭābiqu l-ʿishrūna mukhaṣṣaṣun li-l-muʾtamarāt.
The twentieth floor is reserved for conferences.
صعدنا إلى الشقة العشرين.
ṣaʿidnā ʾilā sh-shaqqati l-ʿishrīn.
We went up to the twentieth apartment.
The feminine noun الشقة still takes العشرين, not a fabricated feminine form. The preposition إلى makes both noun and ordinal genitive.
Compound ordinals from 21st to 99th
For 21st–99th, coordinate the unit ordinal and the decade with و. The unit comes first, just as in cardinal numbers, but it agrees with the noun. In a definite ordinal, both coordinated parts normally take الـ: الحادي والعشرون، الثالثة والأربعون.
صدر القرار الحادي والعشرون صباحا.
ṣadara l-qarāru l-ḥādī wa-l-ʿishrūna ṣabāḥā.
The twenty-first decision was issued this morning.
راجعت الصفحة الحادية والعشرين مرة أخرى.
rājaʿtu ṣ-ṣafḥata l-ḥādiyata wa-l-ʿishrīna marratan ʾukhrā.
I reviewed the twenty-first page again.
جاء فريقنا في المركز ٢٣.
jāʾa farīqunā fī l-markazi th-thālithi wa-l-ʿishrīn.
Our team came in 23rd place.
The digit ٢٣ still means 23; its ordinal reading is unit-first الثالث والعشرون or, after في المركز, genitive الثالث والعشرين. Arabic script direction does not turn it into 32.
Common Mistakes
Applying cardinal gender polarity to an ordinal
❌ قرأت الصفحة الثالث.
Incorrect — ordinals agree normally; feminine الصفحة requires الثالثة.
✅ قرأت الصفحة الثالثة.
qaraʾtu ṣ-ṣafḥata th-thālitha(h).
I read the third page.
Mismatching definiteness
❌ حذفت فصل الثالث.
Incorrect — definite ordinal الثالث must modify definite الفصل in the intended phrase.
✅ حذفت الفصل الثالث.
ḥadhaftu l-faṣla th-thālith.
I deleted the third chapter.
Using a plural noun for “the thirteenth student”
❌ وصل الطلاب الثالث عشر.
Incorrect for ‘the thirteenth student’ — an ordinal identifies one singular member of the sequence.
✅ وصل الطالب الثالث عشر.
waṣala ṭ-ṭālibu th-thālitha ʿashar.
The thirteenth student arrived.
Reversing the value of a written digit
❌ المركز ٢٣ هو المركز الثاني والثلاثون.
Incorrect — ٢٣ is 23rd, not 32nd.
✅ المركز ٢٣ هو المركز الثالث والعشرون.
al-markazu th-thālithu wa-l-ʿishrūna huwa l-markazu th-thālithu wa-l-ʿishrūn.
Position 23 is the twenty-third position.
Missing oblique case on the decade
❌ وصلنا إلى الطابق الخامس والعشرون.
Incorrect — after إلى, the coordinated decade must be genitive العشرين.
✅ وصلنا إلى الطابق الخامس والعشرين.
waṣalnā ʾilā ṭ-ṭābiqi l-khāmisi wa-l-ʿishrīn.
We reached the twenty-fifth floor.
Key Takeaways
- Ordinals are adjectives: they normally follow a singular noun and agree in gender, definiteness, and case.
- Memorize irregular أول/أولى and the defective behavior of ثانٍ/ثانية.
- Compound 11th–19th forms agree in both parts and are normally built on fatḥ.
- The decades use ـون nominative and ـين oblique, with no special feminine decade form.
- In 21st–99th, coordinate a gender-agreeing unit ordinal with the decade and normally repeat الـ on both parts.
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