to sleep
In French, 'dormir' is used to describe the activity of sleeping. It is a regular -ir verb, so it follows standard conjugation patterns. 'Je dors' means 'I sleep', 'tu dors' means 'you sleep' and 'nous dormons' means 'we sleep'. It is used the same way as 'to sleep' is used in English.
I have to sleep early tonight.
This sentence is expressing the speaker's need to go to sleep early in the evening.
You can sleep in the guest room.
In this example, the speaker is giving permission to the listener to go to sleep in the guest room.
They are going to sleep at the hotel tonight.
This case is indicating a future action where the subjects, in this case 'they', will be sleeping at the hotel in the evening.