1. By indicates an actor, instrument, or cause

Pattern: be + past participle + by + noun
The work was done by a carpenter.
The mark was made by a hammer.
The damage was caused by the storm.

2. By means following the boundary of something; along
They walked by the side of the road.

3. By indicates a method or way.

Pattern: verb + (noun) + by + noun
She made a little money by begging.
We sent the letter by air mail.
They went to the mountains by Route 66.

4. By can mean according to a form, period of time, packaging, weight, number, or amount

Pattern: verb + (noun) + by + the + noun
He makes his decisions by the rules.
She charges by the hour.
We buy eggs by the dozen.

Typical nouns after by the: day, hour, month, week job, piece
bag, barrel, box, bucket, bushel, cup, drop, gallon, ounce, pint, pound, quart, ream, tablespoonful, teaspoonful

5. By can mean not later than.
You must be here by six A.M. sharp.
I'm worried; they should have arrived by now.

Expression:
by the time—when
By the time you get up, I'll be in New York.

6. By means near or next to.
His desk is by mine.
I hope you will stay by me.

7. By indicates multiplication, division, and square measurement.
We multiplied four by three. (4 x 3 = 12)
They divided ten by two. (10 + 2 = 5)
That room measures ten feet by twelve feet. It measures 120 square feet.

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