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a.) Accusative πόσον may retain its ancient/classical final accusative -ν in speech, especially before a vowel sound or π, τ, κ. This is also the way you will see this expression written (i.e., as πόσον καιρό) in more formal writing.
For a little more about this issue of the ancient/classical final -ν in the accusative singular, see "FYI: final accusative -ν" and "στη ή στην", both in Discussion Forum 20, the lesson where the masculine and feminine accusative singular is formally introduced..
b) If the question word is an adjective such as πόσος, yes the adjective must always agree in gender, number, and case with its noun, whether that noun is expressed or implied. If, however, the question word is an indeclinable pronoun such as τι; ("what?"), there can be no such inflectional agreement.
c.) The genitive case was historically used to measure amount -- distance, time, weight, price, value -- and can still be seen in this use today in more formal writing. Thus an expression such as Είμαι είκοσι τεσσάρων χρονών is equivalent to "I am [of an extent of time of] twenty four years [old]".
Regards, Greg Brush |