before
be·fore
I
 /bıˈfoɚ/  adv  
  1 : at an earlier time
   Haven't we met before?
   the night/day before
   I've never seen her so happy before. [=I've never seen her as happy as she is now]
   We haven't had these problems before.
   Everything is just as (it was) before.
  2 formal + old-fashioned : to or toward the place where someone is going : in advance
   marching on before [=ahead]
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II
  prep  
  1 a : at a time preceding (something or someone) : earlier than (something or someone)
   We arrived shortly before six o'clock.
   before dinner
   He left just before sunrise.
   I've never seen her so happy before now.
   Call me before your arrival.
   She arrived the day before yesterday.
   Why haven't you ever helped me before now/this?
   I finished the exam before him. [=before he finished the exam]
   You can go before me. [=before I go]
   He's an electrician, like his father before him. [=his father was also an electrician]
   They earned 50,000 dollars before (paying) taxes.
  1 b US
  — used to describe a time earlier than a specified hour
   It's 20 (minutes) before 12. [=it's 20 of/to 12; it's 11:40]
  2 : preceding (something or someone) in order or in a series
   Your name is listed before mine.
   You'll see my house just before the bank and after the school.
   The number 2 comes before 3 and after 1. [=2 comes between 1 and 3]
  3 a : in front of (someone or something)
   The Great Plains stretched endlessly before them.
   The championship fight took place before a crowd of thousands.
  : in the presence of (someone)
   The defendant stood up before the judge.
  — see also (right) before/in front of your (very) eyes at eye, 1
  3 b : being considered by (someone or something)
   The case before the court involves a robbery.
   the candidates before the voters
   I have a proposal to put before [=to] the board.
   The question before us is this: did he fall or was he pushed?
  3 c : in the future for (someone) : ahead of (someone)
   They had no idea of the ordeal that lay before them.
  4 a : in a higher or more important position than (something)
   They put quantity before [=above] quality. [=they cared more about quantity than about quality]
  4 b : rather or sooner than
   He vowed that he would choose death before dishonor. [=he would rather die than be dishonored]
  5 formal : under the force of (something)
   The tree fell before the force of the wind. [=the force of the wind caused the tree to fall]
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III
  conj  
  1 a : earlier than the time that : earlier than when
   He left long before morning came.
   The judge stood up before the defendant did. [=the defendant stood up after the judge did]
   Say goodbye before you go.
   Call me before you arrive.
   Before [=until] she met him she had never been so happy.
   I finished the exam before he did.
   It was/happened not long before he arrived.
   He left before I could thank him. [=I wasn't able to thank him because he left too soon]
   I'll resign before I give in! [=I would rather resign than give in]
  — see also before you know it at know, 1
  1 b : until the time that
   It did not take long before he had earned their trust. [=he earned their trust quickly]
   “I have promises to keep and miles to go before I sleep…” ‒Robert Frost, “Stopping by Woods on a Snowy Evening” (1923)
  2 a
  — used to refer to something that might happen
   Get out of there before you get dirty! [=get out of there because you will/might get dirty if you don't]
   Before I forget, will you give me your telephone number? [=I'm asking for your telephone number now because I might forget to do it later]
  2 b
  — used to say that one thing must happen for another thing to happen or be possible
   He must be convicted before he can be removed from office.
   You must have completed an introductory class before you can take an advanced class.