zenith

the zenith is the direction pointing directly above a particular location (perpendicular, orthogonal). Since the concept of being above is itself somewhat vague, scientists define the zenith in more rigorous terms. Specifically, in astronomy, geophysics and related sciences (e.g., meteorology), the zenith at a given point is the local vertical direction pointing away from the direction of the force of gravity at that location.

For reference, the vertical direction at the given location and pointing in the same sense as the gravitational force is called the nadir. Zenith is the opposite of nadir.

Zenith is also used for the highest point reached by a celestial body during its apparent orbit around a given point of observation. Often used in this sense about the Sun, it only corresponds to the first concept of zenith for one latitude at a time, and never at all for latitudes outside the tropics.