Are there sentences that cannot be changed to active?

In one line

The rule

Only passive sentences with a clear subject (the doer of the action) can be changed to active voice.

Let's understand it simply

Imagine you hear, "The roti was eaten." You do not know who ate it. If you want to change this to active voice, you need to know the person: "Rahul ate the roti." If the sentence does not tell you who did the action, you cannot make it active.

How it works

1. Look for the doer (the person or thing doing the action) in the passive sentence.
2. If the doer is mentioned ("by someone"), you can make it active.
3. If the doer is missing, you cannot make a proper active sentence.
4. Some sentences use words like "It is said..." or "Mistakes were made..." with no doer. These cannot be made active.

The story behind it

English grammar has two voices: active and passive. In active voice, the subject does the action. In passive, the subject receives the action. Sometimes, English leaves out the doer on purpose, especially when the doer is unknown or not important.

Where you see it in real life

• Newspaper headlines: "A new bridge was built." (Who built it? Not mentioned.)
• School announcements: "The exam has been postponed." (Who postponed it?)
• Notices: "Mobile phones are not allowed." (Who does not allow them?)
• Science books: "Water is heated to 100°C." (Who heats it? Not said.)

Why it matters

• You need to know this for writing and editing sentences.
• It helps you understand why some sentences sound formal or distant.
• This rule is tested in English grammar exams.
• It helps you write clear instructions and reports.

Common mistakes

• Trying to change every passive sentence to active, even when the doer is missing.
• Adding a fake subject like "someone" or "people" when it is not in the sentence.

Remember it

If the doer is missing in passive, you can't make it active.