"And what, monks, is aging and death? The aging of beings in the various orders of beings, their old age, brokenness of teeth, greyness of hair, wrinkling of skin, decline of life, weakness of faculties -- this is called aging. The passing of beings out of the various orders of beings, their passing away, dissolution, disappearance, dying, completion of time, dissolution of the aggregates, laying down of the body -- this is called death. So this aging and this death are (together) called aging-and-death. "And what, monks, is birth? The birth of beings into the various orders of beings, their coming to birth, descent (into a womb), production, manifestation of the aggregates, obtaining the bases for contact -- this is called birth."