Passive Agent: Use "Por",

In a normal sentence, the subject does the work. "Juan writes the book." Juan is the star. In a passive sentence, the object becomes the subject. "The book is written by Juan." Now, the book is the star. But Juan is still there! He is the "agent." To connect the action to Juan, we need por. This word acts as a bridge. Without it, the sentence falls apart. It tells your listener exactly who is responsible for the action. It is like a grammar traffic light. It directs the flow of information. If you forget por, people might get confused about who did what. It is a small word with a big job. You use it to give credit where credit is due. Whether it is a book, a meal, or a mistake, por points the finger at the culprit. It is very logical once you see the pattern. It is like putting together a puzzle where por is the final piece that connects the person to the result.

1. 1Building a passive sentence with an agent follows a very specific recipe. Follow these steps to get it right every time:
2. 2Start with the thing receiving the action (the new Subject). Example: La casa (The house).
3. 3Add the verb ser (to be). Make sure it matches the tense and the subject. Example: fue (was).
4. 4Add the Past Participle of your main verb. This is the tricky part! It must match the gender and number of your subject. Example: pintada (painted - feminine/singular to match la casa).
5. 5Add the magic word por (by).
6. 6End with the person or thing doing the action (the Agent). Example: el artista (the artist).
7. 7Put it all together: La casa fue pintada por el artista.
8. 8Remember, the past participle is like a chameleon. If you are talking about los libros (the books), the participle becomes escritos. If you are talking about las cartas (the letters), it becomes escritas. The word por never changes. It is the rock of the sentence. It stays por no matter who or what follows it. It is the easiest part of the whole structure!

When should you pull this grammar tool out of your kit? Use it when the result is more important than the person.

• News and Media: You will hear this on the news constantly. "The law was passed by the government." (La ley fue aprobada por el gobierno).
• History and Art: When talking about who built what or who painted what. "The pyramids were built by the Egyptians."
• Formal Situations: In a job interview, you might say, "This project was led by me." It sounds professional and focused.
• Giving Credit: When you want to make sure someone gets the praise (or blame) they deserve. "The cake was made by my grandmother."
• Real-World Scenarios: Imagine you are at a restaurant and the waiter brings the wrong dish. You might say, "This was not ordered by me!" (Esto no fue pedido por mí). It sounds a bit dramatic, but it gets the point across.

It is also great for literature. If you are reading a Spanish novel, you will see por everywhere in passive descriptions. It adds a layer of formal elegance to your Spanish.

Don't overdo it! If you use the passive voice for everything, you will sound like a robot or a very old textbook.

• Casual Conversations: If you are grabbing coffee with a friend, don't say, "The coffee was ordered by me." Just say, "I ordered the coffee." It is much more natural.
• Quick Directions: When giving directions, keep it active. "Turn right" is better than "The right turn should be made by you."
• Simple Daily Actions: You don't need to say, "The door was closed by me." Just say, "I closed the door."

Think of the passive voice like a tuxedo. It looks great at a wedding or a gala, but you probably shouldn't wear it to the gym. Use it when you want to emphasize the object or sound official. Otherwise, stick to the active voice. Your friends will thank you for not sounding like a 19th-century lawyer.

Yes, even native speakers mess this up sometimes! Here are the pitfalls to avoid:

• Confusing por and para: This is the big one. Para usually means "for" (a goal or destination). Por means "by" (the agent). If you say La carta fue escrita para Juan, it means the letter was written *for* Juan to receive. If you say La carta fue escrita por Juan, it means Juan is the one who wrote it.
• Forgetting Agreement: Beginners often forget to change the ending of the past participle. They might say La casa fue pintado. No! La casa is feminine, so it must be pintada.
• Using the Wrong Verb: You must use ser, not estar. La comida fue preparada (The food was prepared - focus on the action). La comida está preparada (The food is prepared - focus on the state/result). Por only follows the ser version for the passive agent.
• Word Order: Don't put por before the verb. It always comes after the participle and before the person doing the action.

The most common contrast is with the "Passive se". In Spanish, we often say Se venden libros (Books are sold). This is also passive, but notice there is no agent! We don't say who is selling them. If you want to include the agent, you *must* use the ser + participle + por structure.

Another contrast is the active voice.

Active: Gaudí construyó la Sagrada Familia.

Passive: La Sagrada Familia fue construida por Gaudí.

Both are correct, but the second one puts the focus on the famous church.

Also, watch out for the "resultative" state with estar.

Passive: El cristal fue roto por el niño (The glass was broken by the boy - focus on the event).

State: El cristal está roto (The glass is broken - focus on the current condition).