by
used in passives
By is most often used in passive sentences. If something is done or caused by a person or thing, that person or thing does it or causes it.
This view has been challenged by a number of researchers.
I was surprised by his anger.
He was knocked down by a bus.
When an -ed word is used like an adjective to describe a state rather than an action, it is not always followed by by. Some -ed words are followed by with or in.
The room was filled with flowers.
The walls of her flat are covered in dirt.
used with time expressions
If something happens by a particular time, it happens at or before that time.
I'll be home by seven o'clock.
By 1995 the population had grown to 3 million.
Be careful
By can only be used with this meaning as a preposition. Don't use it as a conjunction. Don't say, for example, ‘By I had finished my lunch, we had to leave’. You say ‘By the time I had finished my lunch, we had to leave’.
By can only be used with this meaning as a preposition. Don't use it as a conjunction. Don't say, for example, ‘By I had finished my lunch, we had to leave’. You say ‘By the time I had finished my lunch, we had to leave’.
By the time I went to bed, I was exhausted.
used to describe position
You can use by to say that someone or something is at the side of a person or object.
I sat by her bed.
She lives in a cottage by the sea.
Be careful
Don't use ‘by’ with the names of towns or cities. Don't say, for example, ‘I was by Coventry when I ran out of petrol’. You say ‘I was near Coventry when I ran out of petrol’.
Don't use ‘by’ with the names of towns or cities. Don't say, for example, ‘I was by Coventry when I ran out of petrol’. You say ‘I was near Coventry when I ran out of petrol’.
Mandela was born near Elliotdale.
saying how something is done
By can be used with some nouns to say how something is done. You don't usually put a determiner in front of the noun.
Can I pay by credit card?
I always go to work by bus.
He sent the form by email.
However, if you want to say that something is done using a particular object or tool, you often use with, rather than ‘by’. With is followed by a determiner.
Clean the mirrors with a soft cloth.
He brushed back his hair with his hand.
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You can use by with an -ing form to say how something is achieved.
Make the sauce by boiling the cream and stock together in a pan.
We saved a lot of money by booking our holiday online.