**by** is on the Basic English 850 List.
- near or next to.
*The mailbox is ***by** the bus stop.

- at some time before (the given time).
*Be back ***by** ten o'clock!

- if something is done
**by** somebody, it is done through their action
*The matter was decided ***by** the chairman.
*The boat was swamped ***by** the water.
*He was protected ***by** his body armour.

- if something is created
**by** somebody, they are the creator, author, etc.
*There are many well-known plays ***by** William Shakespeare.

- shows how someone does something
*I avoided the guards ***by** moving only when they weren't looking.

- using the rules or logic of.
*I sorted the items ***by** category.

- with a change of. In this case,
**by** shows how much something has changed.
*Our stock is up ***by** ten percent.

- shows how slowly, or how quickly, someone does something (used in the form "
*X* **by** *X*" or "by *X*s")
*We went through the book page ***by** page.
*We crawled forward ***by** inches.

- When measuring the width and depth of something,
**by** is used between the lengths of the two sides.
*The window is 45 cm ***by** 60 cm.

- If you multiply $x$
**by** $y$ , you multiply $x$ × $y$ .
*Five multiplied ***by** seven is 35.

- If you divide $x$
**by** $y$ , you find how many $y$ s are in $x$ .
*35 divided ***by** seven is five.