Question 1

When should I include "by + agent" in passive voice?

Accepted Answer

Include the agent when it is specific, famous, surprising, or adds important information. For example: "Romeo and Juliet was written by Shakespeare" (famous author), "The equation was solved by a 10-year-old" (surprising), "The building was destroyed by the earthquake" (important cause).

Question 2

When should I omit the agent in passive voice?

Accepted Answer

Omit the agent when it is unknown, obvious, unimportant, or general. Words like "someone," "people," "they" (general), and "one" are typically omitted. For example: "My wallet was stolen" (not "by someone"), "English is spoken worldwide" (not "by people").

Question 3

Is it grammatically wrong to include an unnecessary agent?

Accepted Answer

It is not grammatically wrong, but it is considered poor style to include agents that add no value. Sentences like "The office is cleaned every evening by them" sound unnatural because the cleaner is obvious and unimportant. Good English omits unnecessary information.

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Present Simple Passive

Past Simple Passive

Passive Negatives

Conditionals

Present Perfect

Reported Speech

By Agent in Passive Voice - When to Include or Omit