This is the 11617th most frequent Portuguese word.
penais
"Penais" means "penal" or "related to penalties or punishment."
The word 'penais' is used here as an adjective modifying 'leis', indicating the laws that pertain to criminal matters.
As leis penais devem ser seguidas por todos.
Criminal laws must be followed by all.
In this sentence, 'penais' is again an adjective describing 'códigos', indicating that the topic is criminal codes.
Os códigos penais variam entre diferentes países.
Criminal codes vary between different countries.
Here, 'Penais' acts as a noun referring broadly to aspects related to penal or criminal system policies.