to die: to come to the end of life, whether of the body, in sin, or to an old way of living.
At its core this verb names one thing: the end of life. The basic prefix on the front strengthens the plain word for dying, so it points to death as something completed, a person who has died rather than someone simply fading. Most of its uses are exactly that ordinary: people, animals, even sea creatures stop living.
What makes the word worth studying is how the New Testament writers, above all John and Paul, stretch this one plain word across more than one kind of death at once. The same verb that buries a body can describe a person who dies still cut off from God, or a believer who has died to an old master, or a seed that has to die in the ground before it can grow. The writers do this on purpose, often setting two kinds of death side by side in a single sentence so the reader feels the jolt.
So the senses below are not separate words. They are one idea, the ending of life, carried over from the body to a person's standing before God and to the picture of a seed. Where a verse balances physical dying against a deeper kind, that double force is usually the point, not an accident of translation.