Until

 What is Until?
Until means "up to a particular time".

1. Until as a preposition of time

I waited until 10 o'clock, and then I left.

Let's see the video below:

2. Until as a subordinating counjunction of time

2.1. Until referring to the present or future

Use these verb forms:

Main clause:

 Present Simple

until-clause:

 Present Simple
 Present Perfect

Let's see some examples below:

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(1) "Everything is quiet until the children get home from school." (after that, it's noisy!)

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(2) We'd better stay here until the weather improves.

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(3) We are staying here until the weather has improved.

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Sentences (2) and (3) describe the future. Notice that will cannot be used in the until-clause.

2.2. Until referring to the past

Use these verb forms:

Main clause:

 Past Simple

until-clause:

 Past Simple
 Past Perfect

Let's see some examples below:

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(1) "He was not allowed to work until he had been in the country six months.

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(2) The villagers stayed indoors until the soldiers left.

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(3) The villagers stayed indoors until the soldiers had left.

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Notes:
(1) Until clauses can be "simplified" in written English by omitting the subject and the verb BE:
Leave the pie in the oven until thoroughly cooked.

(2) Usually, we do not say "from ... until ...": we say "from ... to".

I hope this article helps. If you have any question, please leave a comment below.