By + Agent in Passive

Use by to name who does the action only if useful.

Examples

• The book was written by Orwell.

Key rules

• By + agent names who does the action
• Use it only when it adds useful information
• Skip it if the agent is unknown, obvious or unimportant
• The agent comes at the end of the clause

Common mistakes

• The window was broken by someone → The window was broken
• The book wrote by Orwell → The book was written by Orwell