This is the 3952nd most frequent Portuguese word.
idoso
Elderly; an older adult.
In this sentence, 'idoso' is used as a noun to refer to an elderly person.
O idoso caminhava lentamente pela praça.
The elderly man was walking slowly through the square.
Here, 'idosos' is used as a plural noun to refer collectively to elderly individuals.
Respeitar os idosos é essencial em nossa sociedade.
Respecting the elderly is essential in our society.
In this case, 'idoso' functions as an adjective describing the relative as elderly.