Por - On Behalf Of

The logic is straightforward. You are replacing one person with another. Imagine your friend is too shy to speak. You speak "for" them. In Portuguese, you speak por them. It implies an exchange or a substitution. You are the representative. You are the proxy. It is not about giving a gift. That would be para. This is about taking someone's place. It is like a grammar swap. One person steps out. Another person steps in. Por sits right in the middle of that swap. It connects the action to the original person.

1. 1Building sentences with this rule is easy. You just need three parts:
2. 2Start with your subject and verb.
3. 3Add the preposition por.
4. 4Finish with the person you are representing.
5. 5If you use a pronoun, remember the forms:
6. 6por mim (for/instead of me)
7. 7por ti (for/instead of you - informal)
8. 8por ele/ela (for/instead of him/her)
9. 9por nós (for/instead of us)
10. 10por vocês (for/instead of you all)
11. 11por eles/elas (for/instead of them)
12. 12Example: Eu assino por você. (I sign for you).
13. 13Notice how por stays the same. Only the pronoun or name changes. It is like a Lego brick. It fits everywhere.

Use por when you are a proxy. This happens a lot in real life. Imagine you are at a restaurant. Your friend is parking the car. You order food por him. You are acting in his place.

In a job interview, this is useful. Maybe a manager is sick. Another person does the interview por her. They are the substitute.

What about legal documents? Sometimes you have power of attorney. You sign a contract por someone else. You are their legal voice.

Use it for voting too. If you can't go to a meeting, a friend votes por you. They use your voice.

Use it for chores. "I will wash the dishes por you today." You are doing their task. It is a nice way to be helpful. Even native speakers use this constantly. It is the ultimate social lubricant.

Do not confuse this with para. This is the biggest trap. If you buy a gift, use para. "This book is para you." If you do a task, use por. "I wrote the email por you."

Don't use por for destinations. If you are going to Lisbon, use para. Por would mean you are going "through" it. That is a different rule!

Also, don't use it for "because of" here. While por can mean "because of," that is a different context. Here, we stick to "instead of."

Think of it like a traffic light. Para is the destination. Por is the exchange. If you mix them up, people might get confused. They might think you are giving them a person! That would be a very weird gift.

The por vs para mix-up is king. It happens to the best of us.

✗ Eu falo para você (when you mean "instead of you").

✓ Eu falo por você (I am your spokesperson).

Another mistake is using em nome de too much. Em nome de is very formal. It sounds like a royal decree. In a cafe, it sounds silly. Just use por. It is faster and friendlier.

Some learners forget the pronoun forms. They might try to say por eu. That is a big no-no. It must be por mim. It is like wearing socks with sandals. It works, but it feels wrong.

Finally, don't forget the context. If the substitution isn't clear, explain it. But usually, por does the job alone.

Let’s compare por with em nome de.

Por is your everyday tool. It is for friends and family.

Em nome de is for lawyers and kings. Use it for "In the name of the law."

Then there is no lugar de. This means "in the place of." It is very literal. You can say "I am sitting no lugar de Maria." But por is more versatile. It covers the action, not just the seat.

What about em vez de? This means "instead of." You use it for choices. "I want tea em vez de coffee." You wouldn't say "I speak em vez de you." That sounds like you are competing! Por sounds like you are helping.