We use before as a subordinating conjunction. We commonly use before with the past simple tense. It suggests that the second event happened soon after the first one. The before clause, which indicates the second action, can be at the end or at the beginning of the sentence:
- Before she left, she gave everyone a present.
- She gave everyone a present before she left.
before + clause, + clause
clause + before + clause
Before can join one clause to another.
- Before I have breakfast, I spend half an hour doing physical exercises.
- I prefer to do my exercises before I have breakfast.
(In both sentences, the speaker does exercises first and then has breakfast. In the second example, the before-clause is given more importance because it comes at the end. Note the comma in the first example.)
- Before he did military service, he went to university.
(He went to university first.)
- He did military service before he went to university.
(He did military service first.)
With before, we use a present tense if the meaning is future.
- I’ll telephone you before I come. (NOT …
before I will come.)
In clauses with before, we often use present perfect and past perfect tenses to emphasize the idea of completion.
- You can’t go home before I’ve signed the letters. (= … before the moment when I have completed the letters.)
- He went out before I had finished my sentence. (= … before the moment when I had completed my sentence.)
(Note that in sentences like the last, a past perfect tense can refer to a time
later than the action of the main verb. This is unusual.)
We sometimes use before to talk about things that don’t happen (because
something stops them).
- We’d better get out of here before your father catches us.
- She left before I could ask for her phone number.
In a formal style, we often use the structure before … ing.
- Please put out all lights before leaving the office.
- Before beginning the book, she spent five years on research.
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