You use the dual form of a special word.
In Arabic, there is a special way to express the English word both.
The following to words are essential for the construction:
- كِلا: “both”; masculine singular
- كِلْتا: ” both”; feminine singular
They both express the dual (مُثَنَّى) – however, grammatically, they are singular (مُفْرَدٌ)! The only difference between كِلا and كِلْتا is the gender. كِلا is masculine and كِلْتا is feminine.
So far, so good – but where should we put them in a sentence? There are two possibilities.
1st part of the إِضافة. The 2nd part must be a definite, dual noun.
- both men ( كِلَا الرَّجُلَيْنِ)
- both times ( كِلْتا الْمَرَّتَيْنِ)
In this application, both words – كِلَا and كِلْتا – are proper nouns of genus (اِسْمُ عَلَمٍ جِنْسِيٌّ).
Apposition (بَدَلٌ). Placed after a dual noun. You have to add a dual pronoun suffix (ضَمِيرُ الْمُؤَكَّدِ) to كِلَا and كِلْتا respectively.
- both men ( الرَّجُلانِ كِلاهُما)
- both times ( الْمَرَّتانِ كِلْتاهُما)
Let’s focus on the interesting part: the grammar. Both words must agree in gender with the noun or pronoun they refer to. So we match كِلْتا and كِلَا either with…
- the gender of the second part of the إِضافة-construction, i.e., مُضافٌ إِلَيْهِ;
- the gender of the word to which كِلَا or كِلْتا refer. It is the word before them, i.e., مُبْدَلٌ مِنْهُ.
What you need to keep in mind if you use option 1, the إِضافة-construction:
- كِلَا (and كِلْتا respectively) agrees in gender with the noun it modifies – but not in case! What does that practically mean? Well, …
- …when they serve as the first part of the إِضافة and when they are followed by an apparent noun (اِسْمٌ ظاهِرٌ), then they are not inflected for cases.
- However, if they are followed by a pronoun suffix in the إِضافة–construction, they do get inflected!
- كِلَا and كِلْتا are grammatically treated as singular. Thus, a verb, adjective, or noun that relates to them, is either masculine or feminine singular.
What you need to keep in mind if you use option 2 (placed after the word they relate to – in apposition):
- When كِلَا or كِلْتا are combined with a pronoun suffix, you have to mark the case visibly. In the nominative case (مَرْفُوعٌ), they stay as they are. However, in the accusative (مَنْصُوبٌ) or genitive case (مَجْرُور), they will get a visible marker. How can we do that? We change the ا into ي.
- This is similar to the dual of nouns or verbs which also have ا in the nominative case (مَرْفُوعٌ) and a ي in the مَنْصُوب- and مَجْرُور-case.
- So we get كِلَيْهما (“kilayhima”) and كِلْتَيْهما (“kiltayhima”).
Let’s put all that input into sentences. We start with option 1 – the إِضافة-construction.
Both of them are teachers. (.كِلَاهُما مُدَرِّسٌ)
Both men saw her. ( كِلا الرَّجُلَيْنِ رَآها) The verb is used in the third person, masculine, singular – and not in its dual form although we are referring to a dual.
Let’s continue with option 2 – the apposition.
It belongs to both of you (plural). ( هُوَ لَكُمْ كِلَيْكُمْ. هِيَ لَكُمْ كِلْتَيْكُم )
I saw young men, both of them. ( رَأَيْتُ الْفَتَيَيْنِ كِلَيْهُما ) Young men is the direct object (مَفْعُولٌ بِهِ) and has to be in the accusative case (مَنْصُوب) – and so does the apposition.