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by - definition and synonyms


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90% of the time, speakers of English use just 7,500 words in speech and writing. These words appear in red, and are graded with stars. One-star words are frequent, two-star words are more frequent, and three-star words are the most frequent.



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adverb, preposition by pronunciation in British English /baɪ/
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By can be used in the following ways:
as a preposition (followed by a noun): The building was destroyed by fire.
as an adverb (without a following noun): As time went by, things improved.
  1. 1
    used for saying who or what does something
    1. a.
      used, especially with passive verbs, for showing who does something or what causes something
      Injured refugees were treated by a Red Cross doctor.
      The abbey was founded by Henry II in 1170.
      Children are fascinated by the idea of magic.
      a rebellion by separatist guerrilla forces
      damage caused by the storm
    2. b.
      used for saying who wrote a book or a piece of music, who painted a picture etc
      a novel by Graham Greene
      mural paintings by Diego Rivera
  2. 2
    used for saying how something is done
    1. a.
      using a particular method to achieve something
      Reading is taught by traditional methods here.
      The palace balcony is shielded by bulletproof glass.
      Every bit of lace is made by hand (=not using a machine).
      by doing something: By using the Internet you can do your shopping from home.
      by post/phone/fax etc: They exchanged New Year’s greetings by email.
    2. b.
      using a particular method of transport
      by car/train/bus/air etc: Sophie’s parents arrived by taxi.
    3. c.
      using a particular road, path, door etc
      We returned home by a different route.
      She went in by the side entrance.
    4. d.
      using a particular name or title
      Staff generally address each other by their first name.
      The UN refugee agency is known by its initials UNHCR.
    5. e.
      used for saying how you start or finish something
      I’m going to start off by explaining the purpose of our campaign.
  3. 3
    before or until
    1. a.
      not later than a particular time or date
      The meeting should have finished by 4.30.
      Application forms must be received by 31st March.
    2. b.
      during the period until a particular time or date
      By mid afternoon over 5,000 people had visited the exhibition.
      by the time (that): By the time Charlotte was 15, she had already achieved worldwide fame.
  4. 4
    used when saying that something happens in a way that was not planned or intended
    Take care that you don’t shoot one of us by mistake.
    We met quite by chance.
    By a stroke of luck I found the perfect title for my new book.
  5. 5
    used for saying that time passes, or how it passes
    As time went by, people’s attitudes changed.
    The days seem to fly by.
  6. 6
    used for showing how much something has changed, or how much difference there is between things
    House prices rose by an average 23% last year.
    Owen broke the world record by 2.4 seconds.
    See also far
  7. 7
    used for saying that someone or something goes past you
    She walked right by me without saying a word.
    There were angry shouts from the crowd as the president’s motorcade drove by.
  8. 8
    beside or close to someone or something
    She was sitting over there by the window.
    There’s an ashtray just by your elbow.
  9. 9
    according to rules or laws
    Casinos are forbidden by law to contribute to political campaigns.
    In the police force we have to do everything by the rulebook.
  10. 10
    used for showing that something is judged according to certain standards of behaviour, quality etc
    It’s no use trying to judge 18th-century morality by modern standards.
    Her performance was amazing by any standard.
  11. 11
    used for saying that someone stops somewhere for a short time, especially while going to another place
    drop/stop/come by: Why don’t you stop by on your way home from work?
    Peggy dropped by the office this afternoon.
  12. 12
    used for saying which part of a persons body or thing you take in your hand when you hold them
    Taking me by the arm, she led me into the next room.
    Always pick up a CD by the outer edge to avoid damaging the surface.
  13. 13
    used for referring to someones character, job, origin, name etc
    by nature/profession/birth/name etc: She was, by nature, a cheerful and friendly sort of person.
    An American by birth, Cassidy had spent much of his life in Bolivia.
  14. 14
    used in calculations and measurements maths
    1. a.
      used for saying what units of measurement are used
      Floor coverings are priced by the square metre.
      Industrial workers are generally paid by the hour.
      sold by the dozen
    2. b.
      used for giving the size of an area, object, or space by stating its length, width, height etc
      The house has a spacious dining room, measuring 18 feet by 15.
      We are able to offer our readers a fabulous 70 by 50 cm souvenir poster.
  15. 15
    used for showing a gradual process
    1. a.
      used when saying that something happens or changes gradually
      The company grew by degrees until it controlled over 20% of the telecommunications market.
      little by little/bit by bit: Little by little Philip got used to life on the farm.
      day by day/week by week etc: His medical condition is continuing to improve day by day.
    2. b.
      used when things or people do something or are dealt with one after the other
      one by one/stage by stage: One by one the men came forward to receive their medals.
      item by item: The finance committee checks through each document, item by item.



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