“For as the body without the spirit is dead…” (James 2:26).
Though it sounds unusual, biologists struggle with creating a clear and simple definition of death.
To “define” death as “the absence of life” is really not helpful. It immediately leads to the question of “What is life?” and defining “life” in a categorical and concise way is just as elusive as defining “death”.
James 2:26 gives the best and briefest definition of death—it is the separation of the spirit from the body. Death is not the cessation of your existence; it is the historic moment when your spirit and body are no longer together.
Your spirit continues its existence in a realm which cannot be discerned by your body’s physical senses. Hence, the name given it is “Unseen”. The Hebrew word is Sheol; the Greek word is Hades.
Because of your spirit’s absence, your body immediately fails to function and begins to slowly decay back into the dust from which God formed it. Your body will remain in this sleepful state until it hears Christ’s voice and is resurrected (i.e., reunited with your spirit). It is this resurrected/immortal body that you will inhabit forever.
How you live today will not affect the mortality of your body; it will die. However, how you live today does affect the location of your everlasting existence in your immortal body.