Dormition is the Roman Catholic teaching concerning the death of Mary and states that Mary died but that her body did not see corruption--was instead bodily assumed into Heaven (see The Bodily Assumption of Mary). Though there is no official Catholic position on whether or not Mary died, it seems that the Church's teaching is that she did die.
Belief in the glorious destiny of the body and soul of the Lord's Mother after her death spread very rapidly from East to West."1
"Regarding the day, year, and manner of Our Lady's death, nothing certain is known." 2
There is a feast celebrated on August 15 of each year called The Feast of the Dormition.