Be to

How can I use "be to"? I have seen it in examples such as,

• You are not to smoke in here.
• They are to be married soon.

 

We use be to + infinitive when discussing formal or official arrangements or to give formal instructions or orders and your examples illustrate these aspects very well. Further examples might be: The Prime Minister is to make a further visit to Devon next week. We are to receive a pay rise in line with inflation in September. I don't mind her going to Ruth's party but she's not to be back late. You are not to leave this house without my permission. Is that clear?

			The be to + infinitive structure is also frequently used in newspaper, radio and television reports to refer to future events. It expresses near certainty that what is forecast will happen. Study the following: A man is to appear in court later this morning charged with the murder of the footballer, Darren Gough. The Ministry of Trade and Industry has announced that it is to move three thousand jobs out of the capital and re-locate them in the North East. Work is to begin this week on the new bridge across the Nile north of Aswan.

			We often use be to + infinitive in the if-clause in conditional sentences when talking about preconditions for something to happen. Study the following: If we are to catch that train, we shall have to leave now. If I were to increase my offer from five hundred to five hundred and fifty pounds, would you be interested in selling me your car then? If we are to solve the world's pollution problems, we must address environmental issues now.

			Be to + passive infinitive is often used when giving instructions. It is noticeable always on medicine bottles and can be seen on other official notices too: To be taken three times a day after meals. These benches are not to be removed from the changing rooms. No food of any kind is to be taken into the examination room.

			Note that although this structure is used to talk about current and future arrangements and events, it is configurated in present and past tenses - see the above examples. However, be to + perfect infinitive is sometimes used to show that a planned event did not materialise: He was to have appeared in the West End show but broke his collar bone during rehearsals. They were to have picked strawberries this morning, but the torrential overnight rain made the field too muddy. Sammy was to have married Sarah but then Jamie came along and the engagement ring he had given her was returned.

Be to + infinitive is used to express:

• official arrangements:

  The Prime Minister is to visit South Korea next month.
  

• official orders:

  At the end of the course all students are to take a written exam. 

• things that should be done:

  What am I to do?

• a possible aim when saying what should be done to reach it:

  If you are to work here for more than three months, you must have a residence permit.

• prohibition (only in the negative):

  You are not to do that again.

Be to + infinitive can also be used in the past:

Mr Jones was to speak at the meeting. (it was arranged and he did)

But was/were to + perfect infinitive means that the arranged event did not actually happen:

Mr Jones was to have spoken at the meeting, but he had to cancel because of his illness.

Note:
Be to is used to talk about formal or official arrangements, formal instructions, and to give orders.
It is particular common in news reports to talk about future events.
We only use to be + infinitive to talk about things that can be controlled by people:

• We don't know where the meteorite is going to land. (Not... the meteorite is to land.)
• I suppose we will all die eventually. ( Not ... we are all to die.)  

We often use to be + infinitive in if-clauses to say that something must take place first (in the
main clause) before something else can take place (in the if-clause):

• If humans are to survive as a species, we must address environmental issues now.
• The law needs to be revised if justice is to be done.

Compare the use of be + infinitive and the present simple for the future in if-clauses:

• Jones needs to improve his technique if he is to win gold at the next Olympics. And
• Jones has said that he will retire from athletics if he wins gold at the next Olympics.

Signs:
Children are not to be left unsupervised in the museum.

Parents' instructions:
You are not to leave the school without my permission.

Instructions on flasks: (notice the passive)
The medicine is to be taken after meals.
This medicine is to be stored in a cool place.
This food is to be refrigerated after being opened.

In the news:
The European Parliament is to introduce a new law on safety at work.
The Queen is to address the nation this afternoon.
The suspect is to stand trial for murder at the local courthouse in November.

Conditionals:
You must train very hard if you are to defeat the champion.
You need to study day in and day out if you are to keep this scholarship.
You must practice and study very hard if you are to become proficient in English.


Thank you for reading.
I hope this proves useful.
Blessings.