The Verb Have.
The verb Have is used in two ways.
1. As a Transitive verb to mean concrete or abstract sense of possession.
You have a fine car.
This rose tree has white flowers.
I have much work to do.
He has a sore throat.
2. As an Auxiliary Verb.
With the perfect participle of another verb, it forms two more tenses.
(a) The Present Perfect.
I have read this book twice.
(b) The Past Perfect.
You had been there before, hadn’t you?
Have and Had followed by the Infinitive form a common way of expressing obligation or fulfilment (fulfillment) of a promise.
I have to be at school before nine.
Don’t forget that you have to write to your aunt tomorrow.
When have we to be at the station?