In short

Counting in English is the easiest grammar there is: pick a number, put a plural after it, done - “three books”, “twenty books”, “a hundred books”. Arabic asks two extra questions every single time. Which shape does the number itself take - and what does the number then do to the noun behind it? The answers change as you climb: 1-2 behave one way, 3-10 another, everything from 11 to 99 a third, and 100 and 1000 go back to a construct of their own. This is the reason learners who can hold a conversation still stumble on “five students”.

The good news is that there are only those few regimes, they are completely regular, and this lesson gives you all of them. Whatever the regime, the noun after a number has one job - to say what you are counting - though only from 11 upward does traditional grammar give it its own technical name, التَّمْييز, “the specifier”; with 3-10 and with 100 and 1000 that same noun is the مُضافٌ إِلَيْهِ of an ordinary إِضافَة. Learn which shape each band of numbers demands, plus the one strange agreement rule that makes ثَلاثَةٌ go with a masculine noun and ثَلاثٌ with a feminine one, and prices, ages, dates and quantities all open up at once.

The rule

1. The counting words themselves. Arabic writes its figures left to right inside a right-to-left sentence, in either of two competing sets of shapes: the 0-9 you already use (the only set in the Maghreb, and increasingly common elsewhere) or the Arabic-Indic shapes still normal in Egypt and much of the Mashriq. Both are read out as the same full words, and this lesson prints 0-9. The words for 0-10 come in two shapes each (the paradigms are in the next section); 11-19 are two-word compounds; 20, 30, 40 … reuse the sound masculine plural ending you met in lesson 9. The word for 100 is traditionally spelled مِائَةٌ, with an alif that is written but not pronounced - a spelling fossil. The modern simplified spelling مِئَةٌ is now perfectly acceptable and increasingly common; both are read the same way. Pick one and be consistent.

2. Regime one - 1 and 2 come after the noun, as adjectives. This is the opposite of English word order, and the most often forgotten rule of the three. واحِدٌ and اِثْنانِ are not counters at all; they are ordinary adjectives that follow their noun and agree with it in gender, case and definiteness, exactly like any adjective from lesson 8:

• كِتابٌ واحِدٌ - one book
• طالِبَةٌ واحِدَةٌ - one female student
• كِتابانِ اثْنانِ - two books

And here is the practical point: you usually do not say them at all. The noun’s own form already carries the information. كِتابٌ on its own means “a book, one book”, and the dual كِتابانِ (lesson 12) means “two books” without any number word. Add واحِدٌ or اِثْنانِ only when you are stressing the count - “only one book”, “two, not three”.

3. Regime two - 3 to 10 build an إِضافَة with a plural genitive. From three upwards the number jumps in front of the noun and takes charge. The pair is a construct of exactly the kind you learned in lesson 20: the number is the مُضاف and the counted noun is the مُضافٌ إِلَيْهِ, so the noun goes into the plural and into the genitive:

• ثَلاثَةُ كُتُبٍ - three books
• عَشَرَةُ أَيّامٍ - ten days
• خَمْسُ طالِباتٍ - five female students
• تِسْعُ سَنَواتٍ - nine years

Because it is a real إِضافَة, the number loses its tanwīn (ثَلاثَةُ, not *ثَلاثَةٌ) and the noun takes the indefinite genitive ـٍ. And because it is a real إِضافَة, the ة of ثَلاثَةُ is pronounced as a full ت - ثَلاثَةُ كُتُبٍ is heard with a hard ت in the middle, not with the light final -a of pausal ثَلاثَة.

4. The gender flip (التَّذْكيرُ والتَّأْنيثُ في العَدَد). For the numbers 3-10 the number takes the opposite gender marking from the thing it counts. A masculine noun pulls the ة onto the number; a feminine noun leaves the number bare:

• masculine كِتابٌ -> ثَلاثَةُ كُتُبٍ (number carries ة)
• feminine طالِبَةٌ -> ثَلاثُ طالِباتٍ (number has no ة)

This looks perverse and it is; grammar books call it “polarity” and there is nothing to understand, only to drill. Two working notes:

• Judge the gender from the singular, not from the plural’s shape. كُتُبٌ looks nothing like a masculine word, but its singular كِتابٌ is masculine, so the number takes ة. سَنَواتٌ has the feminine plural ending, and its singular سَنَةٌ is feminine, so the number stays bare: تِسْعُ سَنَواتٍ. أَيّامٌ is a broken plural of masculine يَوْمٌ: عَشَرَةُ أَيّامٍ.
• Polarity applies to 3-10 and to the unit part of 13-19 and 23-99. It does not apply to 1, 2, 11 or 12, which simply agree with their noun, nor to the tens or to مِائَةٌ and أَلْفٌ, which never change shape for the gender of what they count.

5. Regime three - from 11 to 99 the noun is singular and accusative. This is the great simplifier. Everything from 11 to 99 takes a singular counted noun in the accusative indefinite, ending in tanwīn fatḥa ـً:

• أَحَدَ عَشَرَ كِتابًا - eleven books (literally “eleven book”)
• إِحْدى عَشْرَةَ طالِبَةً - eleven female students
• عِشْرونَ طالِبًا - twenty students
• خَمْسَةٌ وعِشْرونَ كِتابًا - twenty-five books

One noun, one ending, from 11 all the way to 99. Note the spelling of that ending: an alif is added after the tanwīn fatḥa (كِتابًا، طالِبًا، يَوْمًا) - but not after a ة, and not after a final hamza that already has an alif before it or under it (طالِبَةً، سَنَةً، مَساءً).

6. Why ـً matters more than the other endings. The pronunciation guide told you that in الوَقْف - stopping at the end of a phrase - the case endings are simply not pronounced. The accusative tanwīn is the famous exception: you drop the tanwīn but you keep the alif, and the word ends in an audible long vowel. So عِشْرونَ كِتابًا really is heard with that ending even in relaxed speech, while the ـٍ of ثَلاثَةُ كُتُبٍ vanishes at a pause. Of all the case endings this path prints, this is the one you will genuinely hear on the radio - which makes counting a good place to start training your ear for إِعْراب.

7. Compound numbers 21-99: unit + وَ + ten. Arabic says the small part first, joined with وَ: “five and twenty”. The unit part behaves as it would on its own (so 3-9 keep their polarity), the ten never changes for gender, and the تَمْييز stays singular accusative:

• خَمْسَةٌ وعِشْرونَ كِتابًا - 25 books
• خَمْسٌ وعِشْرونَ طالِبَةً - 25 female students
• واحِدٌ وثَلاثونَ يَوْمًا / إِحْدى وثَلاثونَ لَيْلَةً - 31 days / 31 nights
• اِثْنانِ وأَرْبَعونَ رَجُلًا - 42 men

8. What inflects and what is frozen. Three different behaviours, and you need to keep them apart:

• 3-10 inflect fully, as the first term of an إِضافَة: ثَلاثَةُ كُتُبٍ (مَرْفوع) / قَرَأْتُ ثَلاثَةَ كُتُبٍ (مَنْصوب) / في ثَلاثَةِ كُتُبٍ (مَجْرور). One bare vowel, no tanwīn.
• 11-19 are مَبْنِيّ - frozen. Both halves sit on a fatḥa whatever the sentence does: أَحَدَ عَشَرَ، ثَلاثَةَ عَشَرَ، تِسْعَةَ عَشَرَ - as a subject, as an object or after a preposition alike. The single exception is 12, whose first half is a dual and therefore swings: اِثْنا عَشَرَ (مَرْفوع) but اِثْنَيْ عَشَرَ (مَنْصوب ومَجْرور).
• The tens carry the sound masculine plural ending and swing with it: عِشْرونَ when the phrase is مَرْفوع, عِشْرينَ when it is مَنْصوب or مَجْرور - جاءَ عِشْرونَ طالِبًا but رَأَيْتُ عِشْرينَ طالِبًا. The ن here never drops, because the number is not a مُضاف.

9. 100 and 1000 go back to an إِضافَة - with a singular genitive. مِائَةٌ and أَلْفٌ are ordinary nouns, so they take a construct like any other noun, and their counted noun is singular genitive: مِائَةُ كِتابٍ، أَلْفُ سَنَةٍ، مِائَةُ طالِبٍ. مِائَةٌ is feminine, which is why the hundreds are built with the bare unit: ثَلاثُمِائَةٍ، خَمْسُمِائَةٍ (usually written as one word). أَلْفٌ is masculine and counts normally: ثَلاثَةُ آلافٍ. In a long compound the تَمْييز follows the number nearest to it: مِائَةٌ وخَمْسَةٌ وعِشْرونَ كِتابًا, but مِائَةُ كِتابٍ on its own.

10. “The three books” - counting something definite. All of the above counts indefinite things. To count something already definite, keep the noun with its الـ and put the number after it as an adjective, with الـ of its own and the same polarity:

• الكُتُبُ الثَّلاثَةُ - the three books
• الطّالِباتُ الخَمْسُ - the five female students

11. Asking “how many”. كَمْ from lesson 15 takes exactly the 11-99 pattern - one singular accusative noun straight after it: كَمْ كِتابًا قَرَأْتَ؟ / كَمْ ساعَةً تَعْمَلُ؟ Answer with a full number phrase, or just the number.

Forms & patterns

0-10. The two columns are chosen by the gender of the counted noun’s singular; from 3 upwards the marking is reversed.

Those are the free-standing forms, as you would say them counting aloud. In front of a noun the tanwīn goes (ثَلاثَةُ كُتُبٍ). ثَمانٍ is the one awkward word: before a noun it appears as ثَماني نِساءٍ, with ثَمانِيَ in the accusative.

11-19 - two frozen words, both on a fatḥa. The unit half flips gender (polarity), the عَشَرَ half agrees with the noun directly.

The tens - one word, two forms, no gender at all.

Hundreds and thousands - ordinary nouns, so a construct with a singular genitive.

The four regimes on one page - this is the table to memorise.

Only the 11-99 row is تَمْييز in the strict traditional sense; the other two constructed rows are an ordinary إِضافَة, with the counted noun as its مُضافٌ إِلَيْهِ (rules 3 and 9).

The number 3-10 in all three cases - only the number moves; the مُضافٌ إِلَيْهِ is locked in the genitive, exactly as in any إِضافَة.

Polarity worked out on real plurals - always check the singular.

Examples

Common mistakes

• ثَلاثُ كُتُبٍ -> ثَلاثَةُ كُتُبٍ - the singular is masculine كِتابٌ, so the number takes the ة. Do not judge the gender from the look of the plural.
• ثَلاثَةُ بَناتٍ -> ثَلاثُ بَناتٍ - and the mirror error: بِنْتٌ is feminine, so from 3 to 10 the number goes bare.
• عِشْرونَ كُتُبٍ -> عِشْرونَ كِتابًا - from 11 to 99 the counted noun is singular and accusative. The plural genitive belongs to 3-10 only.
• خَمْسَةُ كِتابٍ -> خَمْسَةُ كُتُبٍ - and the mirror of that: 3-10 demand a plural. A singular here is the 11-99 pattern applied in the wrong band.
• ثَلاثَةُ كُتُبٌ -> ثَلاثَةُ كُتُبٍ - the noun after 3-10 is the second term of an إِضافَة, so it is مَجْرور: tanwīn kasra, never tanwīn ḍamma.
• ثَلاثَةٌ كُتُبٍ -> ثَلاثَةُ كُتُبٍ - the number is the first term of that same إِضافَة, so it loses its tanwīn and keeps one bare vowel.
• واحِدُ كِتابٍ -> كِتابٌ واحِدٌ - 1 is not a counter. It follows its noun like an adjective, and most of the time you simply leave it out.
• اِثْنانِ كُتُبٍ -> كِتابانِ - two of anything is the dual, and the dual says “two” by itself. Add اثْنانِ after it only for emphasis.
• جاءَ عِشْرينَ طالِبًا -> جاءَ عِشْرونَ طالِبًا - the tens really do inflect: ـونَ for the subject, ـينَ after a verb’s object or a preposition.
• أَحَدَ عَشَرُ كِتابًا -> أَحَدَ عَشَرَ كِتابًا - 11 to 19 are frozen on a fatḥa in both halves, in every position in the sentence. Only 12 changes (اِثْنا / اِثْنَيْ).
• مِائَةُ كُتُبٍ -> مِائَةُ كِتابٍ - 100 and 1000 take a singular genitive, not a plural one. The plural pattern stops at 10.

Tips

• Learn 3-10 as pairs, never as single words: ثَلاثَةٌ/ثَلاثٌ، أَرْبَعَةٌ/أَرْبَعٌ، خَمْسَةٌ/خَمْسٌ. Storing one form and deriving the other under pressure never works.
• One sentence holds the core of the system: “up to ten the noun is plural and genitive; from eleven it is singular and accusative; one and two come afterwards”. Say it until it is automatic.
• For polarity, train the reflex “what is the singular, and is it masculine or feminine?” The gender of the plural’s ending is irrelevant - سَنَواتٍ and طالِباتٍ take a bare number because سَنَةٌ and طالِبَةٌ are feminine, not because of the ـاتٌ.
• Drill with two fixed props, one masculine and one feminine - كِتابٌ and طالِبَةٌ - and count from 1 to 25 with each of them out loud. Ten minutes of that beats any amount of reading.
• Listen for the ـًا. After 11 it is the one ending that survives a pause, so a real recording will hand you عِشْرينَ طالِبًا with the ending intact. Use it as free إِعْراب practice.
• Do not swallow the ة of ثَلاثَةُ كُتُبٍ: inside a construct it is a hard ت, and saying it correctly is the quickest way to sound like you know the rule.
• Phone numbers, room numbers and years-as-figures are read digit by digit or as plain numbers with no counted noun at all, so none of this applies to them. That is a lot of everyday numbers you can use today.
• Ignore for now the awkward corners: ثَمانٍ, the long compound thousands, and the fact that a few plurals take a fatḥa instead of a kasra in the genitive. They are lesson 41’s business.