This is the 749th most frequent Portuguese word.
ontem
"Ontem" means "yesterday" in English.
Here, "ontem" indicates a specific moment in the past, referring to the day before today.
Ontem foi um dia cheio de eventos.
Yesterday was a day full of events.
Here, "ontem" is part of a clause that provides a contrast to the overall description of the day's experience.
Apesar de ontem ter chovido, o dia foi agradável.
Even though it rained yesterday, the day was pleasant.
In this sentence, "ontem" is used to set the temporal context of the action described (visiting the museum).