That sentence just made me wonder what would be the gender of the adjectives in those general statements : "It is legal" ; "It is not fair" ; "It is great"... when you are not actually refering to any noun in particular ? Would the neuter gender be prefered ?
It is legal=Είναι νόμιμο, it is not fair=δεν είναι δίκαιο, it is great=είναι υπέροχο. The neuter gender is not only prefered, it is actually the correct gender to use. It is because there is always a "αυτό" implied, with "αυτό" being "the thing that happened/happens now", "the thing we are discussing about" etc
What if you want to add to the question: "...to drink", "...to drive"? is it: "...για να πιω", "για να οδήγησω"?
Could I ask "Ποια είναι η ενηλικιότητα;" as well, or is there a difference in meaning?
"ενηλικιότητα"! Wow, what a word! Lingot for that sir! :)
You could ask "Ποια είναι η ηλικία ενηλικίωσης;" which admittedly sounds a bit repetitive but is the correct way to say it.
Full disclosure: I thought you made up the term "ενηλικιότητα"... I just asked another native Greek speaker; they never heard of it either! Apparently google returns results with it - thank goodness I checked! Most results link to dictionary sites and, as far as I can tell, this is a legal term. So I would suggest against using it, unless you are familiar with the specific context within which it can be used.
Thank you very much for your quick reply. I just started learning Greek some weeks ago and discovered the word 'at random' on google. So I will follow your suggestion, not to use the word until I am familiar with it.