Whenever you have X of Y, the X will have the third person possessive suffix on it, which is going to be one of the following: -ı, -i, -u, -ü, -sı, -si, -su, -sü.
The month of December --> [December] [Month] + -ı, -i, -u, -ü, -sı, -si, -su, -sü.
Month is "ay". You'll see that you need "-ı" when you do the vowel-harmony-calculation: Aralık ayı.
In Turkish, there are definite compounds and indefinite compounds. This is an indefinite compound. When we form a compound noun, like, say "business man," where a noun is defined by another noun, but the relationship is not one of possession (the man is not OWNED by a business, but the word "business" still boils down which kind of man he is), we show this by using the suffix of possession on the second of the nouns, the one which is modified, but not the genetive suffix on the first of the nouns, the one doing the modification.
"Aralık ayı çok sıcak." Translation: December is very hot.
December in the Turkish question & the English answers are not in the (possessive) case. The root word definition only. No attachments, cases or suffixes.
Ektoraskan - His answer has fully explained this.
"The month of December" - Aralık ayı.
Ay - month.
2 ay sonra. Two months later.
I'm sorry for not being able to explain this further.
Ektoraskan - Message of thanks for answering this question & please can your comments have a reply facility? Not sure why it hasn't?
Thank you. I think I got confused when you said it had the possessive suffix on it. I think I followed tsuj1g1r1's answer though.
So we have "Aralık ayı" which is an indefinite compound so we add the -ı to it. Contrast that with "takım elbise" which must be a definite compound?
What makes it indefinite or definite?
A definite compound is one where something is owned by something else. In this case, "December" isn't owned by "month," but if I were to say "the child's apple," the elma would be owned by the coçuk, and so "çocuğun elması" would be a definite compound with both a genetive and a possessive suffix. "Takım elbise" doesn't have a possessive suffix, so I'm not sure where it fits into all this, sorry. :(
I was in Brisbane last week, with 3 German colleagues. There is an Ahmet's kebab restaurant that everyone praises. The Germans told me "Let's go there mate!" - I was like "Wait, 'MATE'? When did you become so Australian?! Plus, I didn't fly 20,000 km to eat Turkish food here." - Then we ate sushi, which as everybody knows is a typical Australian delicacy. Oh well.