This is the 4595th most frequent Portuguese word.
costumam
"Costumam" means "they usually" or "they tend to."
In this sentence, the word 'costumam' indicates a habitual action performed by the subject 'Eles' (They).
Eles costumam ir ao parque aos domingos.
They usually go to the park on Sundays.
Here, 'costumam' is used to express the usual behavior or routine of the students (os alunos).
Os alunos costumam fazer a lição antes da aula começar.
The students usually do the homework before the class starts.
In this case, 'costumam' describes a general tendency or custom observed among 'as pessoas' (people).