The dual is marked by the ان / ين  ending in nouns, adjectives and demonstratives:

– the nominative dual of كتاب  is كتابانِ  and the accusative/genitive كتابيْنِ

– the nominative dual of هذا  is هذانِ  and the accusative/genitive هذَيْنِ

– the nominative dual of هذه  is هاتان  and the accusative/genitive هاتينِ

 

ا  in pronouns: 

– the two of you (regardless of gender): أنتما  ; the corresponding pronoun suffix is كما

– the two of them (regardless of gender): هُما  ; the corresponding pround suffix is هما  as well. 

Note: 1. There is no specific pronoun for “the two of us”, 2. Though the pronouns do not differentiate in gender, the verbs do (see below).

 

and ان / ا  in verbs:

– the two of you write (regardless of gender): تكْتُبان  and past tense: كَتَبْتُما

– the two of them (masculine) write: يكْتُبان  and past tense: كَتَبا

– the two of them (feminine) write: تكْتُبان  and past tense: كَتَبتا