This is the 2256th most frequent Spanish word.
mensuales
Monthly.
The word 'mensuales' is used as an adjective describing the frequency of 'pagos' (payments) as occurring every month.
Los pagos mensuales son necesarios para mantener el servicio.
Monthly payments are necessary to maintain the service.
Here 'mensuales' is an adjective modifying 'informes' (reports), indicating that these reports are issued monthly.
Los informes mensuales contienen datos detallados de las operaciones.
The monthly reports contain detailed data of the operations.
In this case, 'mensuales' qualifies 'clases' (classes), meaning these are scheduled with a monthly frequency.