Numbers 11-99: Gender Agreement

From 11 to 99 the number has two parts:

• 11: أحد عشر with masculine nouns, إحدى عشرة with feminine ones.
• 12: اثنا عشر / اثنتا عشرة as the subject, اثني عشر / اثنتي عشرة as the object or after a preposition.
• 13-19: the unit is reversed as in 3-10, but عشر agrees: ثلاثة عشر طالبا (13 male students), ثلاث عشرة سنة (13 years); 18 feminine is ثماني عشرة.
• 21-99: unit + و + tens. 1 and 2 agree (واحد / إحدى, اثنان / اثنتان), 3-9 are reversed: خمسة وأربعون عاما, أربع وثلاثون طاولة.
• Tens end in ون as the subject and in ين as the object or after a preposition: عشرون / عشرين.

The counted noun stays singular: طالبا، سنة.