Questions & Answers about Çocuğun notu çok iyi.
Why is it çocuğun and not 'çocukun'?
The root word for child is çocuk. When we add a suffix starting with a vowel, like the genitive suffix -un, the hard consonant k softens to a ğ (soft g). This is a common rule called consonant mutation.
How do we choose the exact genitive suffix -un for the word çocuk?
We follow 4-way vowel harmony. The last vowel in çocuk is u, so the suffix needs to match it. That gives us -un instead of -ın, -in, or -ün.
Why does the word not (grade) have a -u at the end?
In Turkish, creating a possessive relationship requires a suffix on both words. The owner (çocuk) gets the genitive suffix, and the owned thing (not) gets a possessive suffix. You are literally saying 'the child's his-grade'. The -u is the 3rd person possessive suffix. Also, not just happens to look like the English word, but it means 'grade' or 'note'!