This is the 67th most frequent Portuguese word.
deve
"Deve" means "must," "should," or "owes" in English, depending on context.
Here, "deve" expresses a sense of obligation or recommendation.
Você deve estudar para o exame amanhã.
You should study for the exam tomorrow.
In this case, "deve" suggests a possibility or a logical deduction.
O céu está nublado, isso deve indicar chuva.
The sky is cloudy; this might indicate rain.
Here, "deve" indicates prohibition with a sense of authority or rule.