The grammar of numbers in Arabic is widely considered one of the most complex topics in the language. Numbers interact with their counted nouns through intricate rules of gender agreement, grammatical case, and singular/plural form that differ depending on the number range.
Numbers 1-2 are straightforward: they agree with the counted noun in gender and follow it as adjectives. واحد/واحدة (one) and اثنان/اثنتان (two) simply describe the noun: رجلٌ واحدٌ (one man), امرأتانِ اثنتانِ (two women).
Numbers 3-10 introduce the famous "gender polarity" rule: the number takes the opposite gender of the counted noun. If the noun is masculine, the number is feminine, and vice versa. The counted noun comes after the number in the genitive plural form: ثلاثةُ رجالٍ (three men — ثلاثة is feminine form despite "men" being masculine), ثلاثُ نساءٍ (three women — ثلاث is masculine form despite "women" being feminine).
Numbers 11-99 have their own set of rules. The counted noun after these numbers is in the singular accusative form: أحدَ عشرَ كتابًا (eleven books — كتابًا is singular accusative). Numbers 13-19 follow the gender polarity rule for the first part, while the second part (عشر/عشرة) agrees in gender with the noun. The numbers 11 and 12 have special forms that must be memorized.
Numbers 100 and above are simpler: the counted noun follows in the singular genitive: مائةُ كتابٍ (one hundred books), ألفُ طالبٍ (a thousand students). These rules may seem daunting, but Ilm Al Lughah breaks them down into manageable lessons with plenty of practice exercises and flashcard drills to build your confidence.