meaning of "of age"

[Sirius Kase]

No: HPFGUIDX 43260

Ali said:- 
> Whilst canon may yet prove me wrong, I must respectively disagree
> with you (Banjoken). In the UK the phrase "coming of age", or "of age" has a
> quite specific meaning which is legally defined as at 18 years old
> (formerly 21). According to my trusty dictionary this means to
> reach  adult status. Whilst I accept that the WW might use different
> phrases  to mean different things, I can't think of any other phrases
> off the top of my head (though please feel free to show me!) I think
> that the average Brit (be they wizard or muggle) would phrase a
> sentence differently if it meant that they hadn't reached the
> relevant age (but not the age of majority). For example, if you were
> 16 and  moaning that you couldn't take your driving test yet:
> You wouldn't be told you're not of age, but you're not old enough.
> Molly uses the same phrase "You're not of age" when replying to the
> twins complaints about not being able to apparate (p 63 GoF UK
> edition). Of course, this doesn't really help in establishing the
> meaning of "of age", as your argument (or mine) would be equally
> valid. But it is a further use of the phrase outside the tournament
> context.
> Ali

In the US "of age" similarly means that a person isn't legally old enough.
It normally isn't used outside of a legal context.  That's my experience at
least.  Now the age itself depends on the activity being regulated.
Drinking has a different legal age than driving.  And as someone mentioned,
different states have different ages.  Being a teenager/young adult can be
very confusing to a person who travels and wants to engage in "adult"
activities.  Another activity with a legal age limit is entering into
legally binding contracts.  In the UK, do young people receive all rights of
adulthoods at the same age?

When I read that part of GoF, my first impression was that the age limit of
17 referred specifically to the Triwizard and that the age line matched for
that reason and not a generic age of adulthood.  I figured that the use of
the legal sounding "of age" was to impress upon the youngsters that this
limitation was not to be taken lightly.  After further pondering, I also see
how this phrasing goes with the later explanation that entering the
tournment is entering into a binding contract.  But, there is a problem with
that, the 14 year old Harry isn't old enough under any law I'm familiar with
to enter into a binding contract.  It seems odd to me that under Wizarding
Law, he would be bound by such a contract unless the contract was not
between him and the cup but between the school and the cup.

Sirius Kase