Zenith

The zenith (UK: /ˈzɛnɪθ/, US: /ˈziːnɪθ/)[1][2] is the imaginary point on the celestial sphere directly "above" a particular location.

The word zenith derives from an inaccurate reading of the Arabic expression سمت الرأس (samt al-raʾs), meaning "direction of the head" or "path above the head", by Medieval Latin scribes in the Middle Ages (during the 14th century), possibly through Old Spanish.

[3] It was reduced to samt ("direction") and miswritten as senit/cenit, the m being misread as ni.

In Islamic astronomy, the passing of the Sun over the zenith of Mecca becomes the basis of the qibla observation by shadows twice a year on 27/28 May and 15/16 July.

When at the zenith the right ascension of the star equals the local sidereal time at your location.

Diagram showing the relationship between the zenith, the nadir , and different types of horizon
Angles and planes of a celestial sphere
The shadows of trees are the shortest on Earth when the Sun is directly overhead (at the zenith). This happens only at solar noon on certain days in the tropics , where the trees' latitude and the Sun's declination are equal.