by Definitions and Synonyms

adverb, preposition

UK /baɪ/

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
used for saying who or what does something
1. 1a
  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. 1b
  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
used for saying how something is done
1. 2a
  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. 2b
  using a particular method of transport
  by car/train/bus/air etc:
  Sophie’s parents arrived by taxi.
  Synonyms and related words
  Booking on and travelling by transport
  aboard
  afloat
  aisle seat
  ...
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3. 2c
  using a particular road, path, door etc
  We returned home by a different route.
  She went in by the side entrance.
4. 2d
  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.
  Synonyms and related words
  Relating to names and the process of naming
  after
  assignment
  better known as
  ...
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5. 2e
  used for saying how you start or finish something
  I’m going to start off by explaining the purpose of our campaign.
3
before or until
1. 3a
  not later than a particular time or date
  The meeting should have finished by 4.30.
  Application forms must be received by 31st March.
  Synonyms and related words
  General words referring to time
  then
  all
  last
  ...
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2. 3b
  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.
  Synonyms and related words
  During a particular period of time
  during
  within
  throughout
  ...
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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
used for saying that time passes, or how it passes
As time went by, people’s attitudes changed.
The days seem to fly by.
Synonyms and related words
General words referring to time
then
all
last
...
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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
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
beside or close to someone or something
She was sitting over there by the window.
There’s an ashtray just by your elbow.
Synonyms and related words
Next to, near to and not far away
local
close
nearly
...
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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.
Synonyms and related words
According to something
according to
under
by
...
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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.
Synonyms and related words
Words used to describe standards
standard
average
high
...
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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.
Synonyms and related words
Function words referring to location
about
across
after
...
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12
used for saying which part of a person’s 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
used for referring to someone’s 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
used in calculations and measurementsmaths
1. 14a
  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. 14b
  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.
  Synonyms and related words
  General words used to describe size
  by
  disproportionate
  double
  ...
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15
used for showing a gradual process
1. 15a
  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. 15b
  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.

phrases

(all) by yourself/itself/himself etc

have a child/baby/son/daughter by someone

Definition and synonyms of by from the online English dictionary from Macmillan Education.

This is the British English definition of by.View American English definition of by.

Change your default dictionary to American English.

View the pronunciation for by.

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