How to Use "By" and "With" in English Grammar

"This task is done by the boy, and he did this with his instruments."

In the two sentences above, you can easily find the prepositions by and with. These two prepositions are very common and are used frequently when you speak and write. That is why it is important to learn how to properly use them.

How to use "By"

Use by when you need to indicate the doer of an action.

 Take the above example: "This task is done by the boy." The doer is the boy.

Here, by clearly points out the boy as the doer.

How to use "With"

Use with when you need to point out an instrument or tool used to complete an action.

Example: She killed the cockroach with a stick.

Here, with points to the stick (the instrument).

More Examples:

The tiger was killed by the hunter with a gun.

The rat was killed by the cat.

The project was completed by Billi with a laptop.