Overview
The agent is the person or thing that performs the action in a passive sentence, introduced by 'by': The letter was written by the manager. The agent is often omitted when it is unknown, obvious, or unimportant. Including the agent shifts focus back to the doer and adds specificity.
The Agent (by + noun)
- definitionThe agent is the person/thing performing the action.
- structurePassive subject + be + past participle + by + agent.
- exampleThe novel was written by Orwell.
- includeInclude 'by' when the agent is important or surprising.
- omitOmit 'by' when unknown, obvious, or unimportant.
Include vs Omit Agent
- includeThe Mona Lisa was painted by Leonardo da Vinci. (important)
- omitThe car was stolen last night. (unknown)
- omitThe letter was signed. (obvious)
- omitMistakes were made. (vague — often evasive)
- includeThe law was passed by Parliament. (specific)
Common Mistakes
- ❌ It was done from the team → ✅ by the team.
- ❌ Overusing 'by' → omit when agent is irrelevant.
- ❌ It was written by someone → better to omit 'by someone'.
When to use
Attribution
The symphony was composed by Beethoven.
Unknown Agent
The documents were leaked last week.
Legal Writing
The contract was breached by the defendant.
Scientific Reports
The experiment was conducted by the research team.