Zenith On the International Space Station, "zenith" and "nadir" are used instead of "up" and "down", referring to directions within and around the station, relative to the earth. Zenith The zenith is an imaginary point directly "above" a particular location, on the imaginary celestial sphere. "Above" means in the vertical direction opposite to the apparent gravitational force at that location. The opposite direction, i.e. the direction in which gravity pulls, is toward the nadir. The zenith is the "highest" point on the celestial sphere. The word "zenith" derives from an inaccurate reading of the Arabic expression (), meaning "direction of the
Opposite (semantics) Opposite (semantics) In lexical semantics, opposites are words lying in an inherently incompatible binary relationship, like the opposite pairs "big : small", "long : short", and "precede : follow". The notion of incompatibility here refers to the fact that one word in an opposite pair entails that it is not the other pair member. For example, something that is "long" entails that it is not "short". It is referred to as a 'binary' relationship because there are two members in a set of opposites. The relationship between opposites is known as opposition. A member of a pair of opposites can