For a formal, arranged plan (the kind you read in news or official notes), use is / are to + the base verb. It sounds official, like an announcement. The same form can also give a formal instruction (an order from above). Form: is / are + to + base verb. Negative: is / are not to + base verb — a formal ban (you must not). Question:Is / Are + subject + to + base verb? Because it is a formal register, keep be to for official notices and reports, not casual talk.
is / are to + verb
The minister is to visit the school next week. (a planned event)
The two companies are to merge in May. (a planned event)
You are to report to reception on arrival. (an instruction: you must)
Visitors are not to feed the animals. (a formal ban)
Are we to wait here? (asking about the official arrangement)
Not "The meeting will to start at three." — say "The meeting is to start at three.". Use is to + the base verb, not "will to".
Try it: A formal notice reads: All staff ___ attend the briefing on Monday. (are to / will to / are about) Answer: are to — For an official, arranged plan, use are to + the base verb: are to attend. "Will to" is not a real form. "Are about" needs "to" and means something different (any second now), which doesn't fit a Monday plan.
is / are about to + verb
For something that will happen any second now, use is / are about to + the base verb. Don't drop the to. This one is neutral in register — fine in speech and writing. Form: is / are + about to + base verb. Negative: is / are not about to + base verb — often a firm refusal (I'm not about to apologize = I certainly won't). Question:Is / Are + subject + about to + base verb?
Hurry, the train is about to leave.
Be quiet, the film is about to start.
I was about to call you when you texted.
I'm not about to give up now. (I firmly refuse to)
Is the meeting about to end? (asking if it's imminent)
Not "We are about leave now." — say "We are about to leave now.". Always keep the to: about to + the base verb.
Try it: Quick, sit down, the show ___ begin. (is about to / is about / is due) Answer: is about to — Something that happens any second now takes is about to + the base verb: is about to begin. "Is about" drops the needed "to". "Is due" also needs "to" and means scheduled for a set time, not this very moment.
is / are due to + verb
For something scheduled for a set or expected time — a timetable, a booking, a plan with a clock or calendar behind it — use is / are due to + the base verb. It means this is the time it is meant to happen, even if that time is still hours or days away. It is common and slightly formal, the natural choice for transport, deliveries, and official schedules. Form: is / are + due to + base verb. Negative: is / are not due to + base verb (not scheduled until later). Question:When is / are + subject + due to + base verb?
The train is due to arrive at 9:15. (that's the scheduled time)
The results are due to be published on Friday. (the set date)
She isn't due to start until next month. (not scheduled before then)
When is the parcel due to be delivered? (asking the scheduled time)
Not "The bus is due arrive in ten minutes." — say "The bus is due to arrive in ten minutes.". Keep the to: due to + the base verb.
Try it: Each one fits a different kind of future. The flight is still two hours away, but on the timetable it ___ land at 6 p.m. (is due to / is about to / is to about) Answer: is due to — For something scheduled to happen at a set time, use is due to + the base verb: is due to land at 6 p.m. "Is about to" would mean any second now, not a fixed schedule. "Is to about" mixes two patterns and isn't real.
is / are set to + verb
Use is set to or are set to with the base verb for something widely expected to happen, where nobody has published a time for it. It is the form news reports reach for when they are passing on a forecast or a briefing: prices are set to rise, the team is set to sign a new player. The expectation is what matters, so it usually sits next to its source, such as analysts, forecasters or sources close to the company.
Temperatures are set to drop sharply this weekend, forecasters say. (predicted, not timetabled)
The company is set to announce job cuts, according to sources. (expected, no date given)
House prices are set to fall for a third year. (a forecast)
Not "The 6:15 train is set to leave from platform 2." — say "The 6:15 train is due to leave from platform 2.". A printed timetable is a schedule, so it takes is due to. Keep is set to for what people expect rather than what a timetable fixes.
Try it: No date has been announced, but analysts say the bank ___ cut interest rates later this year. (is set to / is due to / is about to) Answer: is set to — If you chose is due to, that claims a published date, and the sentence says none has been announced. Something expected by analysts with no fixed time takes is set to. "Is about to" would mean within moments, not later this year.
Telling the three apart
Same future, three different angles — pick by the basis, not by feel. is to = an official, arranged plan or an order from above; formal register, the language of announcements and notices. is about to = it will happen this very second (imminence); neutral register. is due to = it is scheduled for a set or expected time (a timetable or booking). Quick test: Is it official / an instruction? → is to. Is it happening right now, this moment? → is about to. Is there a set time on a schedule? → is due to.
The president is to address the nation tonight. (official, arranged plan)
Sit down — the play is about to begin. (this very second)
The ferry is due to leave at noon. (the timetable time)
Not "Quick, the kettle is due to boil over!" — say "Quick, the kettle is about to boil over!". Happening this second = about to; due to needs a set scheduled time.
Try it: Everyone went quiet as the singer stepped up to the microphone and ___ start. (was about to / was due to / was to) Answer: was about to — This is the very-next-moment meaning (imminence), so use be about to: was about to start. be due to would need a set scheduled time on a timetable; be to would signal an official arranged plan or an order — neither fits 'stepped up and, any second, began.'