Adversative Conjunctions (Mas, Porém, Contudo) | Portuguese (Brazil) Grammar

Adversative conjunctions (conjunções adversativas) all do one thing: signal that what follows opposes, qualifies, or corrects what came before. English funnels almost all of this through "but" and "however"; Portuguese spreads it across a graded set — from the everyday spoken mas up to the formal written contudo and não obstante. Choosing the right one is mostly a matter of register and position, not meaning. This page maps the set, explains the crucial difference between fixed mas and mobile porém, and isolates the genuinely tricky word senão. For a focused three-way comparison, see Mas vs Porém vs Contudo.

The set, graded by register

Conjunction	Gloss	Register	Notes
mas	but	neutral / spoken	the default; fixed position
porém	but, however	neutral–formal	mobile, behaves like an adverb
contudo	however, yet	formal / written	mobile
todavia	however, nevertheless	formal / literary	mobile
no entanto	nonetheless, however	formal / written	mobile
entretanto	however / meanwhile	formal	also = "in the meantime"
não obstante	nevertheless	very formal / legal	mobile

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For everyday speech, "mas" covers virtually everything. As you move up in formality — an email, an essay, a legal brief — swap in "porém," then "contudo / no entanto," then "não obstante." They're nearly synonymous; the choice signals how formal you're being.

mas — the core

mas is the unmarked, all-purpose contrast word, equally at home in conversation and writing. It is a true coordinating conjunction: it sits fixed at the boundary between the two clauses and cannot move.

Eu queria ir, mas estava cansada demais.

I wanted to go, but I was too tired.

O carro é bonito, mas gasta muita gasolina.

The car is good-looking, but it burns a lot of gas.

In casual speech mas often stacks with other particles for emphasis — mas que, mas é, mas então — and Brazilians sometimes pronounce/spell it mais by mistake (a homophone trap covered below).

Mas que dia horrível!

What an awful day! (emphatic 'mas que')

porém — mobile, adverb-like

porém means the same thing but behaves differently: it is deslocável — it can slide to different positions in the second clause, like an adverb, set off by commas. This mobility is exactly what mas lacks.

Eu queria ir; porém, estava cansada.

I wanted to go; however, I was tired. (porém at the front)

Eu queria ir; estava, porém, cansada demais.

I wanted to go; I was, however, too tired. (porém slid inside the clause)

O projeto é ambicioso. Não temos, porém, orçamento para ele.

The project is ambitious. We don't, however, have the budget for it.

You cannot do this with mas: ❌ Estava, mas, cansada is impossible. So the rule of thumb is: if you want the contrast word anywhere but the clause boundary, you need porém (or contudo, todavia, no entanto), not mas.

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"porém" and friends typically take a comma (or semicolon) before AND, when mid-clause, after. "mas" takes a comma before it and nothing after. This punctuation difference is a quick visual tell for which word a writer chose.

contudo, todavia, no entanto, entretanto

These four are the formal/written register. They are also mobile like porém. They differ only in flavor:

contudo and no entanto — neutral formal, very common in essays and journalism.
todavia — a touch more literary.
entretanto — formal contrast, but beware: it also means "meanwhile / in the meantime," so context disambiguates.

O relatório aponta crescimento; contudo, os custos subiram.

The report points to growth; however, costs rose. (formal/journalistic)

A teoria é elegante. Todavia, falta-lhe comprovação empírica.

The theory is elegant. Nevertheless, it lacks empirical proof. (literary/academic)

As vendas caíram. No entanto, a empresa manteve os empregos.

Sales fell. Nonetheless, the company kept the jobs. (formal)

Ele viajou. Entretanto, a equipe seguiu trabalhando.

He traveled. Meanwhile/However, the team kept working. ('entretanto' = either; context decides)

For the text-organizing use of these connectors across paragraphs, see Contrast Markers.

senão — the special one

senão is not a synonym of mas. It is the odd member of the family, with two distinct meanings, neither of which is plain "but":

(1) "otherwise / or else" — introducing the bad consequence if the first clause fails. Often after a command.

Corra, senão você vai perder o ônibus.

Run, or else you'll miss the bus.

Estuda, senão você reprova.

Study, otherwise you'll fail.

(2) "except / but (rather)" — meaning "anything other than," typically after a negative.

Não quero nada senão paz.

I want nothing but peace. (= nothing except peace)

Ela não faz outra coisa senão reclamar.

She does nothing but complain.

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Test for "senão": can you replace it with "or else" (consequence) or "except / but rather" (exclusion)? If yes, it's "senão." If the word means plain "but" (simple contrast), it's "mas." Note "se não" written as two words means "if not" — a different thing entirely: "Se não chover, vamos à praia" = "If it doesn't rain, we'll go to the beach.")

ao passo que — contrast of parallel facts

ao passo que ("whereas / while") is a subordinating contrast word: it sets two facts side by side to highlight their difference, rather than overturning the first. (It is subordinating, so it lives at the edge of this group.)

O Norte é úmido, ao passo que o Nordeste é seco.

The North is humid, whereas the Northeast is dry.

English comparison

English does the work of this entire set with mainly two words — "but" (the mas slot) and "however / nevertheless / yet" (the porém / contudo slot). The single most useful insight for an English speaker: "however" is mobile and "but" is fixed, exactly like porém vs mas. You'd never write "I was, but, tired," and you'd never write estava, mas, cansada; but "I was, however, tired" and estava, porém, cansada both work. So map "but" → mas and "however / nevertheless" → porém / contudo, and the positional rules transfer almost for free.

Common Mistakes

❌ Eu queria ir, mais estava cansada.

Incorrect — 'mais' means 'more'; the contrast word is 'mas' (a homophone trap).

✅ Eu queria ir, mas estava cansada.

I wanted to go, but I was tired.

❌ Estava, mas, muito cansada.

Incorrect — 'mas' is fixed and cannot sit mid-clause; use mobile 'porém.'

✅ Estava, porém, muito cansada.

I was, however, very tired.

❌ Corra, mas você vai perder o ônibus.

Incorrect — for 'or else' you need 'senão,' not 'mas.'

✅ Corra, senão você vai perder o ônibus.

Run, or else you'll miss the bus.

❌ Se não chover vamos à praia, escrito 'senão.'

Incorrect — 'if not' is two words 'se não'; 'senão' (one word) means 'otherwise/except.'

✅ Se não chover, vamos à praia.

If it doesn't rain, we'll go to the beach.

❌ Bater um papo com o chefe, todavia ele estava ocupado.

✅ Fui bater um papo com o chefe, mas ele estava ocupado.

I went to chat with the boss, but he was busy.

Key Takeaways

The adversative set — mas, porém, contudo, todavia, no entanto, entretanto — all signal opposition; they differ mostly by register (spoken mas → formal porém/contudo).
mas is a fixed coordinating conjunction; porém (and the formal ones) are mobile, behaving like adverbs and taking commas on both sides when mid-clause.
senão (one word) is the special member: "otherwise / or else" or "except / but rather" — never plain "but." Don't confuse it with two-word se não ("if not").
Watch the homophone mas ("but") vs mais ("more").
Map English "but" → mas (fixed) and "however / nevertheless" → porém / contudo (mobile); the positional rules carry over.

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