In very simple words, death is the end of life.
For human being, life is the existence of an individual.
In this simple definition another term is required in order to be explained and that is -life. So, in medical science, death is the permanent and irreversible cessation of all vital functions namely the brain function, the respiratory function, and the circulatory or heart function. Accordingly the medical definition further elaborates the two the usual aspects definition, ‘end’ and ‘existence’. Integrating the abovementioned two aspects, death can be very rationally and scientifically defined as the absolute disappearance of functioning. With all that said… With ethical and philosophical points, in the science of psychology or psychiatry theology is also included, to have the problems comprehensive. Theological or religious sides of death is supposed to be important And therefore the definition of death for a Muslim must be the absolute disappearance of the functions for the time period in between the two lives -one before death and another after death, if we integrate the scientific aspect with the description. Islam defines death as a mandatory transitional event in between the ‘life before death’ and ‘life after death’. Then again, when he truly believes in Islam, it can be easily assumed that death becomes a less stressful event for a Muslim.
In our boring life death is related with the biggest stresses as long as the knowledge -death ends.