before: adverb, conjunction

before (adverb)

1 We can use before to mean 'at any time before now'.
We use it with a present perfect tense (have + past participle).

• Have you seen this film before^?
  


• I've never been here before

Before can also mean 'before then', 'before the past time that we are talking about'.
We use a past perfect tense {had + past participle).

• She realized that she had seen him before

2 In expressions like three days before, a year before, a long time before, the meaning is 'before then'.
We use a past perfect tense.

• When I went back to the school that I had left eight years before, everything was different.

before (conjunction)

clause + before + clause
before + clause, + clause

1 We can use before to join two clauses.

We can either say:

• A happened before B happened


• OR Before B happened, A happened.

The meaning is the same: A happened first.

Note the comma (,) in the second structure.

• I bought a lot of new clothes before I went to America.


• Before! went to America, I bought a lot of new clothes.
  


• He did military service before he went to university. ( = He did military service first.)


• Before he did military service, he went to university. ( = He went to university first.)

2 In a clause with before, we use a present tense if the meaning is future.

• I'll telephone you before you leave (NOT . . . before you will leave.)

3 In a formal style, we often use the structure before + -ing.

• Please put out all lights before leaving the office.


• Before beginning the book, he spent five years on research.