Usages of caso
À noite, fecho as cortinas e ligo a ventoinha, mesmo que esteja frio, caso o vizinho faça barulho.
At night I close the curtains and turn on the fan, even if it is cold, in case the neighbour makes noise.
Caso eu esteja muito cansado amanhã, vou ficar em casa a estudar português.
If I am very tired tomorrow, I will stay at home studying Portuguese.
Elon.io is an online learning platform
We have an entire course teaching Portuguese grammar and vocabulary.