When I wrote a romantic letter some time ago to my girlfriend in Boa Vista, the first line in her response was “nossa!”
When I showed my book to my friend Djenifer, in Campo Verde, Mato Grosso, she said “nossa!” with her eyes widening and lighting up in amazement.
The Portuguese word nossa!, is an interjection which corresponds to the English “wow!” or “My God, how beautiful!”.
The word “nossa” (without the exclamation) could also mean “ours”, if you use it as a pronoun.
I’ve noticed that while the English interjection “wow!” is used to express both pleasant and unpleasant surprises or bursts of emotions, the Portuguese expression “nossa!” is used only for pleasant surprises or bursts of emotions.
On the other hand, the expression “opa!” is used for less pleasant situations.
(Related: Meu Deus, que forca!)