Of all the preposition contractions in Brazilian Portuguese, the ones built on por are the most disguised. Where de + o becomes the transparent do, and em + o becomes the obvious no, por + o becomes pelo — a word that looks nothing like its parts. English speakers routinely fail to recognize that pelo, pela, pelos, and pelas are just por plus an article in a costume. This page demystifies that costume, shows you exactly when the fusion is mandatory (always, with the article) and when it is forbidden (with pronouns and demonstratives), and explains the historical accident that produced the odd-looking form.
The four forms
There are exactly four contractions, and every one of them is obligatory in modern Brazilian Portuguese. There is no uncontracted alternative — "por o" and "por a" simply do not exist in correct writing or speech.
| por + | article | contraction | example |
|---|---|---|---|
| por + o | masc. sing. | pelo | pelo correio (by mail) |
| por + a | fem. sing. | pela | pela manhã (in the morning) |
| por + os | masc. plur. | pelos | pelos campos (through the fields) |
| por + as | fem. plur. | pelas | pelas ruas (through the streets) |
Mandei o pacote pelo correio na sexta.
I sent the package by mail on Friday.
A gente costuma caminhar pela praia no fim da tarde.
We usually walk along the beach in the late afternoon.
Why it looks so different: the per + lo story
The strangeness of pelo has a historical explanation worth knowing, because it makes the form stick. Old Portuguese had a preposition per ("through, by") alongside por. The definite articles were once lo, la, los, las (you can still see this in Spanish el/la/los/las and Italian lo/la). When per met lo, they fused: per + lo → pelo. Over time, the standalone per merged into por, but the contracted form kept the old p-l skeleton.
So pelo is a fossil: it preserves a preposition (per) and an article shape (lo) that have otherwise vanished from the language. The initial consonant of the article — that l — is the giveaway that you are looking at a contracted article, not a random word. (The noun o pelo, "the body hair / fur," is an unrelated homograph; context always disambiguates.)
As decisões importantes são tomadas pelos diretores.
The important decisions are made by the directors.
Fiquei sabendo da promoção pela minha colega.
I found out about the promotion through my coworker.
The frozen time expressions
Two of the most common phrases in everyday Brazilian speech are contractions you will use daily: pela manhã, pela tarde, pela noite (in the morning / afternoon / night). Note that these are not the only way to say "in the morning" — Brazilians very often say de manhã instead — but pela manhã is fully natural and slightly more deliberate in tone.
Prefiro estudar pela manhã, quando a casa está silenciosa.
I prefer to study in the morning, when the house is quiet.
O voo chega pela manhã e a reunião é só à tarde.
The flight arrives in the morning and the meeting is only in the afternoon.
Passei pelas suas redes sociais e vi as fotos da viagem.
I went through your social media and saw the trip photos.
The crucial exception: pronouns and demonstratives do NOT contract
Here is where por behaves differently from de and em, and where English speakers who have learned the contractions of de and em get tripped up. With de and em, fusion spreads beyond the article: de + ele → dele, de + isso → disso, em + ele → nele, em + isso → nisso. With por, this does not happen. Por contracts only with the definite article. With everything else — personal pronouns, demonstratives, indefinite articles — it stays stubbornly separate.
| por + | result | compare with de |
|---|---|---|
| por + ele | por ele (no fusion) | de + ele → dele (fuses) |
| por + isso | por isso (no fusion) | de + isso → disso (fuses) |
| por + aquilo | por aquilo (no fusion) | de + aquilo → daquilo (fuses) |
| por + um | por um (no fusion) | de + um → dum (optional) |
The reason is partly the same history: the contraction lives in that old per + lo welding, which only ever applied to the definite article. The pronouns and demonstratives never had the l-initial shape that triggered the fusion, so they were never absorbed.
Fiz tudo isso por ele, mas ele nem agradeceu.
I did all of this for him, but he didn't even say thanks.
Estava chovendo muito; por isso a gente não saiu.
It was raining a lot; that's why we didn't go out.
Ela é apaixonada por aquilo que faz.
She is passionate about what she does.
Bare nouns stay separate too
The contraction needs an actual article. When por introduces a bare, article-less noun — common in abstract causes and means — there is nothing to contract with, so it stands alone: por amor, por dinheiro, por telefone, por e-mail, por acaso.
Ele aceitou o emprego por dinheiro, não por vocação.
He took the job for money, not out of calling.
A gente combinou tudo por telefone mesmo.
We arranged everything just by phone.
Common Mistakes
❌ Mandei o currículo por o e-mail da empresa.
Incorrect — por + o is mandatory and becomes pelo.
✅ Mandei o currículo pelo e-mail da empresa.
I sent my résumé through the company's email.
❌ Por as ruas do centro tinha muita gente.
Incorrect — por + as must contract to pelas.
✅ Pelas ruas do centro tinha muita gente.
Through the downtown streets there were lots of people.
❌ Fiz isso pele ele, porque ele pediu.
Incorrect — por does NOT contract with pronouns; pelo is por+o only.
✅ Fiz isso por ele, porque ele pediu.
I did this for him, because he asked.
❌ Não foi de propósito, foi pelo acaso.
Incorrect — 'acaso' has no article here; it stays por acaso.
✅ Não foi de propósito, foi por acaso.
It wasn't on purpose, it was by chance.
❌ Briguei com ela e pisso parei de falar com ela.
Incorrect — por isso never fuses into one word.
✅ Briguei com ela e por isso parei de falar com ela.
I fought with her and that's why I stopped talking to her.
Key Takeaways
- por + o/a/os/as always fuses into pelo / pela / pelos / pelas — mandatory, never "por o."
- The odd shape comes from the old preposition per plus the archaic article lo (per + lo → pelo).
- Unlike de and em, por contracts only with the definite article — por ele, por isso, por aquilo, por um all stay separate.
- A bare noun with no article (por amor, por telefone) gives nothing to contract with.
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Start learning Portuguese→Related Topics
- Preposition 'Por': By, Through, For (cause)A2 — How 'por' marks cause, means, path, duration, exchange, and the passive agent — and why it always contracts with the article into pelo/pela.
- Complete Contractions ReferenceA2 — The master grid of every preposition contraction in Brazilian Portuguese — which fusions are obligatory, which are optional, and which prepositions never contract at all.
- Por vs Para: Decision GuideA2 — The forward-pointing para (goal, destination, recipient, deadline) versus the backward-pointing por (cause, path, means, exchange) — with decision tests and minimal pairs.
- Passive SentencesB1 — Building passive sentences in Brazilian Portuguese — the ser-passive with 'por', the se-passive for agentless statements, and why everyday speech prefers active recasts.