"The day is Thursday."
Translation:O dia é quinta-feira.
Hope it can help you a little: http://www.soportugues.com.br/secoes/morf/morf26.php
I didn't even know there were irregular words. I thought if a word ends on o or a that's always what does in front
I tried using está here and it was marked wrong. Can anyone explain why ser is used in this situation?