Mal vs. Mau in Portuguese: Tell the Adverb from the Adjective
Mau describes a noun; mal usually describes how an action happens or how someone feels.
Real Life Portuguese · 6 min read · Updated October 14, 2026
The short answer
Mau is an adjective meaning bad or unpleasant. It agrees with the noun: mau, má, maus, or más.
Use mau to describe a noun
If you can replace the word with bom or boa (good), mau or má is usually the matching form.
Foi um mau momento para conversar.
It was a bad moment to talk.
Ela teve uma má impressão do lugar.
She had a bad impression of the place.
Eles não são maus profissionais.
They aren’t bad professionals.
Use mal to describe an action or state
Mal often works as an adverb and means badly or poorly. It can also appear in expressions such as passar mal (to feel unwell).
If the sentence describes how someone did something, mal is often the form you need. If it describes the noun itself, use the adjective mau or má.
Dormi mal ontem.
I slept badly last night.
A impressora está funcionando mal.
The printer is working poorly.
Ele passou mal depois da viagem.
He felt unwell after the trip.
Use a quick substitution check
Try replacing mal with bem (well) or mau with bom (good). The opposite often reveals whether you need an adverb or an adjective.
The check is a learning shortcut, not a substitute for meaning. Memorize common expressions as a whole phrase.
Ela fala mal alemão.
She speaks German poorly.
O atendimento foi mau.
The service was bad.
Ele chegou mal-humorado.
He arrived in a bad mood.
Put it into practice
For each sentence, ask whether the word describes a noun (mau/má) or how something happens (mal).
Quick practice
Which Portuguese example matches “I slept badly last night”?
Choose an answer to check yourself.
Keep practicing with the Real Life Portuguese app
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