Be to in English expresses instruction or command:
You are to do exactly as I say.
– You must do exactly what I tell you.
Be to is also used in English when speaking about an action or event that is planned, most often officially:
The President is about to visit Rome.
– The President is expected to visit Rome. (or The President is to visit Rome.)
Be about to / Due to are used in English when speaking about actions or events that are expected to happen very soon:
The building is due to be completed soon.
– The building is to be completed soon.
He is about to announce the result.
– He is expected to announce the result.
More articles on English grammar
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