- The plane mid-way between the zenith and the nadir which in a flat landscape divides earth from sky. Not to be confused with the event horizon, as found in black holes.
- The apparent intersection of the earth and sky, as perceived from any given position.
- The same illusion as it might be portrayed in a perspective drawing.
- As seen from a given location, the junction at which the earth, or the sea, appears to meet the sky. Also called apparent horizon, or visible horizon.
- A horizon (1) as seen from an antenna transmitting site. Such a horizon is the furthest distance that a direct wave may travel. It is the line that is formed by the points at which the direct waves from a radio transmitter become tangential to the surface of the earth. Due to atmospheric refraction, this horizon extends beyond the apparent horizon. Also called radio horizon.
- noun a line in the far distance, on which the sky and ground appear to meet
Origin & History of “horizon”
Etymologically, the horizon is simply a ‘line forming a boundary’. The word comes via Old French orizon and late Latin horīzōn from Greek horī́zōn, a derivative of the verb horīzein ‘divide, separate’ (source also of English aphorism (16th c.), originally a ‘definition’). this in turn came from the noun hóros ‘boundary, limit’. Horizontal (16th c.), which came either from French or directly from late Latin, originally meant simply ‘of the horizon’; it was not until the 17th century that it began to be used in its modern sense ‘flat, level’.