any construct getting formal when they get shorter? Normally, when you shorten a phrase, then they feel like informal or colloquial. I heard that 'be to' construct is the short form of 'be going to' in somewhere else. So I was wondering if there's any example of this kind of transition.
1: She is going to be home by midnight
...is normally a straightforward predictive assertion equivalent to...
1a: She will be home by midnight.
2: She is to be home by midnight
...normally carries the strong implication that...
2a: She is required to / must be home by midnight
This second form is often used when the speaker himself is the person imposing the requirement / giving the order, but it can also be used where the "requirement" (to be home by midnight, or whatever) is imposed by someone else, circumstances, "Fate", etc.