Understanding as knowledge of suffering (Buddhism)

On the Path of Purification of Hinayana Buddhism, panna (understanding) is considered as of one kind (monad), of two kinds (dyads), of three kinds (triads) or of four kinds (tetrads). There are five dyads, four triads and two tetrads. All have the characteristic of penetrating the individual essences or true nature of states (monad). In the first tetrad, this is one of the four kinds of understanding as knowledge of the four noble truths.