This is the 355th most frequent Portuguese word.
alto
"Alto" in Portuguese means "tall" or "high."
Here, 'alto' is used as an adjective meaning 'tall', describing the building's height.
O prédio mais alto da cidade é impressionante.
The tallest building in the city is impressive.
In this instance, 'alto' functions as an adjective meaning 'loud', describing the volume of the sound.
O som do rádio está muito alto.
The sound of the radio is very loud.
Here, 'alto' is used as an adverb meaning 'high', describing the action of climbing.