I'm reading a novel and a character says this line:''you ARE to be back here before dark'' but I could not find this usage of the verb to be in my dictionary, so here I ask you if this is informal English for saying ''you MUST or HAVE TO be back before dark''.
I would say that similar language could be used in some sort of specification document, so it's reasonably formal. And it is an imperative statement.– Hot LicksFeb 14, 2015 at 13:18
Is the all-caps "ARE" in the original?– phenryFeb 16, 2015 at 17:21
It's grammatical, and means what you say, but as regards register lies towards or at the other extreme, being formal to highly formal:
be to [do something] FORMAL
1 used for telling someone what to do
You are to stay here until I send for you.
... All books are to be returned by Friday.
A confusable usage is
3 used for saying or asking what should be done
What are we to do?
You are to be congratulated on your wise decision.
1In my dialect, it's a stern admonition, not necessarily a formality. You're to be home by midnight, no ifs, ands, or buts!– TRomanoFeb 14, 2015 at 12:35
I've adjusted slightly, but still consider it always in the formal half of the continuum, usually near the extreme. I'm sure most parents would say 'I want you back by ...' / 'Be home by ...' / 'You must be home by ...' .... Perhaps it's less marked in Scotland. Feb 14, 2015 at 13:09
Could be dialect difference. In my neck of the woods, "You must be home by midnight" is a command the teenager can meet with a non-committal blank look; whereas "You're to be home by midnight" is a demand which expects at least a nod of assent.– TRomanoFeb 14, 2015 at 17:12