subject to death: alive now, but bound to die
Greek used this adjective for the whole class of living things that die, as against the gods who were thought not to. It says nothing about how long a life lasts or how it will end. It names a condition: being within death's reach. So it is not the same as calling someone νεκρός, "dead." A mortal body is alive at this moment, and the word tells you what it is heading toward.
The New Testament uses it only six times, all in Paul's letters, and the pattern is tight:
- it always describes a body or its flesh, never a soul or a spirit
- it always sits next to a promise of life, whether life given now or a body raised later
- it is always said of human beings, never of God or of the risen Christ
Twice Paul lets the adjective stand on its own, so that "what is mortal" becomes almost a name for the human condition: the thing that has to be clothed with ἀθανασία, "immortality," or be swallowed up by life. Its positive opposite is ἄφθαρτος, "imperishable," and its near neighbor is φθαρτός, "perishable," which describes the same body from the angle of wearing out and rotting rather than of dying. Where θάνατος names death itself, this word names the creature standing under it.