If I understood it correctly, "ابنَك" is the form used when you're talking to a male who has a son, and "ابنِك" when you're talking to a female who has a son. The pronoun forms "you/your" are gender neutral in English, but in Arabic you have different forms of "you" depending on the gender of your interlocutor. But other users have pointed out that the vowels chosen by Duolingo are not appropriated in current dialects or standard Arabic.
It is not a question of gender here, but a question of whether "son" is the subject of the sentence or not. - In our case, "son" is the subject, so the correct form is "ibnUk" - It could have been 'ibnAk" if "son" was the object (ex: you saw people: "وَرَأَيْتَ النَّاسَ") - A word lasts with "I" after some prepositions like: Major prepositions: li - لِـ = to (in order to) / bi - بِـ = with, by means of / ka - كَـ = like (for comparison) / fî - في = in / min - مِنْ = from (origin or material) / 3an - عَنْ = about, regarding /alâ - عَلى = on / 'ilâ - إِلى = to (destination) / Hattâ - حَتَّى = until / wa - وَ : and Other prepositions: /mundu - مُنْذُ : since / ma3a - مَعَ = with / 3inda - عِنْدَ = to localize an object that someone possess: "عِنْدَ الْوَلَدِ كُرةٌ" means the boy has a ballon Link (in French): https://monsieurboursier.fr/arabe/grammaire/particule/preposition.html
- As to the gender, what changes is not the vowel of the noun but he vowel of the pronoun targeted, so here the letter "k" Translation of "your apple": For a female: tufahatuki For a male: tufahatuka It follows the same logic as "Anti" (you for female) or "Anta" (you for male)
@ArabicFrench - you are 100% correct. Ibnuka = your son (nominative, when addressing a male); Ibnuki = your son (nominative, when addressing a female). But that's in fusHa or MSA. But @Prof.David is also correct. In spoken dialects, the fatHa or the kasra on the kaf (Ibnuka or Ibnuki; denoting whether addressing a male or female), is shifted to the final consonant of the noun itself and it becomes Ibnaka = your son, when talking to a male or Ibnika = your son, when talking to a female. This makes the noun's case indeterminate. But hey, this is spoken dialect now. Convenience matters more than 100% exact grammar! :-)
Thank you very much, as a North African dialect speaker I really did not know that rule of Middle Eastern dialect! (in our dialect sometimes we don't even bother to make the grammatical difference between a male or a female x) ) It really shows to what extent fusHa Arabic and dialects are very different! Thanks
Thank you very much, Rajas Daithankar, for explaining this so well. Other contributors have simply criticised Duolingo and corrected eg ibnak/ibnik to ibnuka/ibnuki without explaining why, leaving us ignoramuses in the dark and puzzled why Duolingo was teaching us "wrong". But now that we know the reason for it, we all feel much happier.