Physical Death
When most people refer to death, they almost always mean the death of the body, which is caused by the separation of the body from the eternal spirit. The apostle James in Chapter 2, verse 26 tells us that "The body without the spirit is dead." The body returns to dust or to the element from which it was created, while the spirit goes to the world of spirits to await personal resurrection. Jacob refers to physical death as "the grave."
Connotation—What death really means
Many people view death as a tragedy, often because they believe the person has been annihilated or that at least they'll not see them again, but Latter-day Saints, while they mourn for the loss of their loved one, view death in a different light. Wilford Woodruff, a great LDS prophet, said, "A great many believe that when a man dies that is the end of him, that there is no hereafter. Can any sensible man believe that the God of heaven has created two or three hundred thousand million spirits, and given them tabernacles [physical bodies], merely to come and live upon the earth and then to pass away into oblivion and to be annihilated? It seems to me that no reflecting man can entertain such belief. It is contrary to common sense and to serious reflection." So while Latter-day Saints sorrow for the loss of companionship of their loved one, they are consoled that the one lost in death has made a "gain, for it is the march of progress, advancement and development." Death to a Latter-day Saint means separation from one state and transition to another—from death in the pre-mortal state to birth in the mortal state, and likewise, from death in the mortal state to birth in the immortal state. They also believe that the hereafter is better than here, the place of trials and tests, particularly if a person has lived up to his or her understanding of what is right. "If mortality be the perfect state, then death would be a frustration, but the gospel teaches us that there is no tragedy in death, but only in sin ("Blessed are the dead that die in the Lord" D&C 63:49). Seen in that light Latter-day Saints find it impossible to grieve for a righteous person who has died, for they have left a world of adversity and sorrow and entered a happier place and condition. To them to grieve that someone has died would be like grieving because someone has graduated from college, leaving the stress of studies, tests, and scrimping behind them. In addition, Latter-day Saints believe that their relationships with the "departed" may continue in the hereafter because family members may be sealed to each other eternally. Other relationships may also continue.
Introduction of Physical Death to Earth
Latter-day Saints believe that death first came to the world through the Fall of Adam ("For as in Adam all die, even so in Christ shall all be made alive" 1 Cor. 15:21-23), and that the Resurrection from death comes through the Savior's Atonement. In addition they believe that there is only one physical death because after people die they are resurrected and can die no more (Alma 11:42-45). Death is part of the gospel plan, and so should not be dreaded or feared.