to be dead: to have died already, so that death is now an accomplished fact.
Greek had a whole family of words for death, and this verb is the old, plain one at its center. In the New Testament, though, it turns up only in forms that look back on a death already accomplished and report the condition it left behind. So in practice this word never says "he dies" or "he is dying"; it says "he is dead." The act of dying belongs to the far more common ἀποθνῄσκω, and the two verbs divide the work between them. Mark 15:44 puts them side by side in one sentence: Pilate is astonished that Jesus is already dead, then asks the officer whether he had died some time ago.
That is why this word keeps appearing at exactly the moment someone needs to settle a fact:
- A messenger tells Jairus his daughter is dead, so there is no point troubling the teacher.
- The soldiers look at Jesus on the cross and see that he is already dead, so they do not break his legs.
- The crowd at Lystra drags Paul out of the city, assuming he is dead.
- Festus describes to Agrippa a certain Jesus who was dead, whom Paul insisted was alive.
In none of those places is the question how the person died. The question is whether death has happened.
From there the word slides easily into naming the person rather than the condition: the dead man carried out of the town gate at Nain, the dead man who walks out of the tomb at Bethany still bound in his burial cloths. The word becomes the label for someone in the state it describes.
Once, in 1 Timothy 5:6, it steps off the physical plane: the widow who lives for her own pleasure "is dead while she lives." Nothing about the word itself has changed. It is still the ordinary word for being dead, now aimed at a life that has lost whatever makes a life alive.