If something is done by a person or thing, that person or thing does it.
The feast was served by his mother and sisters...
I was amazed by their discourtesy and lack of professionalism...
If you say that something such as a book, a piece of music, or a painting is by a particular person, you mean that this person wrote it or created it.
...a painting by Van Gogh...
'Jacob's Ladder', the newest film by Adrian Lyne, is a post-Vietnam horror story.
If you do something by a particular means, you do it using that thing.
We'll be travelling by car.
...dinners by candlelight.
If you achieve one thing by doing another thing, your action enables you to achieve the first thing.
Make the sauce by boiling the cream and stock together in a pan...
The all-female yacht crew made history by becoming the first to sail round the world...
You use by in phrases such as 'by chance' or 'by accident' to indicate whether or not an event was planned.
I met him by chance out walking yesterday...
He opened Ingrid's letter by mistake...
If someone is a particular type of person by nature, by profession, or by birth, they are that type of person because of their nature, their profession, or the family they were born into.
I am certainly lucky to have a kind wife who is loving by nature...
She's a nurse by profession and now runs a counselling service for women...
If something must be done by law, it happens according to the law. If something is the case by particular standards, it is the case according to the standards.
Pharmacists are required by law to give the medicine prescribed by the doctor.
...evening wear that was discreet by his standards.
If you say what someone means by a particular word or expression, you are saying what they intend the word or expression to refer to.
Stella knew what he meant by 'start again'...
'You're unbelievably lucky.' — 'What do you mean by that?'
If you hold someone or something by a particular part of them, you hold that part.
He caught her by the shoulder and turned her around...
She was led by the arm to a small room at the far end of the corridor...
Someone or something that is by something else is beside it and close to it.
Judith was sitting in a rocking-chair by the window...
Felicity Maxwell stood by the bar and ordered a glass of wine...
If a person or vehicle goes by you, they move past you without stopping.
A few cars passed close by me...
He kept walking and passed by me on his side of the street.
If you stop by a place, you visit it for a short time.
We had made arrangements to stop by her house in Pacific Grove...
Daddy called and asked me to drop by his office.
If something happens by a particular time, it happens at or before that time.
By eight o'clock he had arrived at my hotel...
We all knew by then that the affair was practically over.
If you do something by day, you do it during the day. If you do it by night, you do it during the night.
By day a woman could safely walk the streets, but at night the pavements became dangerous...
She had no wish to hurry alone through the streets of London by night.
In arithmetic, you use by before the second number in a multiplication or division sum.
...an apparent annual rate of 22.8 per cent (1.9 multiplied by 12)...
230cm divided by 22cm is 10.45cm.