|Until is a word that can function as a preposition and as a conjunction. As a conjunction, it means up to the time or the event mentioned. Until is the same as till , which means we can use them interchangeably like in these examples:|
The little boy waits patiently until/till his father gets home.
We cannot have dinner until/till we finish our home work.
Notice that in the sentences above, the present tense is used to refer to a time in the future. To show the completion of a task or action, Present Perfect and Past Perfect tenses can be used as in this sentence: The teacher told the students that they cannot leave the room until they have finished their seat work
To can also be used in place of until and till when used as a preposition. The following sentences use to in place of until and till.
The baker works from 5am to 3pm.
Erica can run fast fro her house to the park.
Please take not that to cannot always be used in place of until. In this sentence: Denzel works until 9pm, the preposition to cannot be used.
Take note that until and till can be used only when we talk about time and not distance. We cannot say: My father can run until 4 kilometers. The correct expression is: My father can run up to 4 kilometers.