be to

Short definition from Wiktionary

Verb

1. 1
   Used to express an official plan, arrangement, or scheduled event.
2. 2
   Used in the past tense to indicate that something was supposed to happen or was destined to happen.
3. 3
   Used after if to introduce a condition that must be met in order for something to happen or succeed.
4. 4
   Used to give commands, instructions, or to state rules. In negative form, it expresses prohibition.
5. 5
   Used to ask or state what someone should do.
6. 6
   Used to ask how something is possible or achievable
7. 7
   Used after if or in inversion to describe hypothetical or imagined scenarios.