Nadir is employed during remote sensing of the atmosphere, as well as when an astronaut faces the Earth while performing a spacewalk. The term nadir can also be used to represent the lowest point reached by a celestial body during its apparent orbit around a given point of observation. This can be used to describe the location of the Sun, but it is only technically accurate for one latitude at a time and only possible at the low latitudes. The sun is said to be at the nadir at a location when it is at the zenith at the location's antipode
Opposite (semantics) has no word that stands in opposition to it (hence the unanswerability of "What is the opposite of platypus?"). Other words are opposable but have an accidental gap in a given language's lexicon. For example, the word "devout" lacks a lexical opposite, but it is fairly easy to conceptualize a parameter of devoutness where "devout" lies at the positive pole with a missing member at the negative pole. Opposites of such words can nevertheless sometimes be formed with the prefixes "un-" or "non-", with varying degrees of naturalness. For example, the word "undevout" appears in Webster's dictionary of 1828, while