death: the end of life, whether the event of dying or the state of being dead
This is the ordinary word for death in the Hebrew Bible. It covers both the moment a person stops living and the lasting condition that follows, and the same form is used for a death already past (the time after someone died) and a death still feared or threatened. Hebrew rarely separates the act of dying from the state of being dead the way English can, so context, not the word itself, tells you which is in view.
From this plain sense the word spreads in two natural directions. Because death is the worst thing that can happen, it becomes a measure of severity: something can be bitter, strong, or certain as death, and a punishment can simply be called death. And because dying is the gateway out of life, the word easily slides toward the place and power that lie on the far side of it, which the next meaning gathers up.
The contrast Hebrew draws most sharply is between death and life. To set life and death before someone (Deuteronomy 30:15) is to set the whole of blessing against the whole of ruin, so the word often carries far more weight than the bare biological fact.