This is the 8613th most frequent Portuguese word.
acumulam
"Acumulam" means "they accumulate" or "they gather."
Here, "acumulam-se" is used as a reflexive verb, indicating that the leaves gather or collect together in a place.
As folhas secas acumulam-se no quintal durante o outono.
Dry leaves accumulate in the backyard during autumn.
In this sentence, "acumulam" is used to denote that the workers are collecting or gathering extra hours through continued action.
Os trabalhadores acumulam horas extras durante a semana.
The workers accumulate extra hours during the week.
"Acumulam" is used here to describe the process of gathering or increasing knowledge over time as a result of study.