Questions & Answers about Çocuklar portakal suyu içiyor.
Why is it portakal suyu instead of just portakal su?
This is an indefinite noun compound, which is used when one noun describes another (like "orange juice" or "bedroom"). In Turkish, you leave the first noun plain (portakal) and add a 3rd person possessive ending to the second noun (su). It literally translates to "orange its-juice".
I thought the buffer letter for the possessive ending was "s" after a vowel. Why is it suyu and not susu?
You are exactly right about the normal rule! However, the word su (water/juice) is a famous exception in Turkish. Whenever su gets a possessive ending, it uses the buffer letter "y" instead of "s". That is why it becomes suyu.
Since the subject "çocuklar" is plural, why doesn't the verb have a plural ending (içiyorlar)?
In Turkish, when the subject of the sentence is a plural human (like çocuklar), adding the plural suffix -lar to the verb is optional. Saying Çocuklar portakal suyu içiyor with a singular verb is perfectly correct and sounds very natural.
Why doesn't portakal suyu have the accusative case ending?
We only use the accusative case (which would make it portakal suyunu) when the direct object is specific, like "the orange juice". Because the children are just drinking orange juice in general, it is an indefinite direct object and does not take the accusative case ending.