zero

indicating the absence of any or all units under consideration

“a zero score”

of or relating to the null set (a set with no members)

a mathematical element that when added to another number yields the same number

adjust (as by firing under test conditions) the zero of (a gun)

“He zeroed in his rifle at 200 yards”

the point on a scale from which positive or negative numerical quantities can be measured

a quantity of no importance

adjust (an instrument or device) to zero value

having no measurable or otherwise determinable value

“the goal is zero population growth”

indicating an initial point or origin

the sight setting that will cause a projectile to hit the center of the target with no wind blowing