horizon

ho•ri•zon n.

Astronomy[countable] the line or circle that forms what seems to be the boundary between earth and sky.
on the horizon, at the limit or range of knowledge, progress, or the like:A cure for that disease is now on the horizon.
Usually, horizons. [plural] the scope or range of a person's interest:Her horizons expanded when she lived abroad for a year.

ho•ri•zon n.

Astronomythe line or circle that forms the apparent boundary between earth and sky.
Astronomy
- the small circle of the celestial sphere whose plane is tangent to the earth at the position of a given observer, or the plane of such a circle (sensible horizon.)
- the great circle of the celestial sphere whose plane passes through the center of the earth and is parallel to the sensible horizon of a given position, or the plane of such a circle (celestial horizon.)
the limit or range of perception, knowledge, or the like.
Usually, horizons. the scope of a person's interest, education, understanding, etc.:His horizons were narrow.
Geologya thin, distinctive stratum useful for stratigraphic correlation.
Geology, Agricultureany of the series of distinctive layers found in a vertical cross section of any well-developed soil.

Latin horizontem, accusative of horizōn
Middle French
Greek horízōn (kýklos) bounding (circle), equivalent. to horíz(ein) to bound, limit + -ōn present participle suffix (nominative singular); replacing Middle English orizonte
Latin horizōn
1540–50

Collins Concise English Dictionary © HarperCollins Publishers::

horizon /həˈraɪz^ən/ n

Also called: visible horizon, apparent horizon the apparent line that divides the earth and the sky
- Also called: sensible horizon the circular intersection with the celestial sphere of the plane tangential to the earth at the position of the observer
- Also called: celestial horizon the great circle on the celestial sphere, the plane of which passes through the centre of the earth and is parallel to the sensible horizon
the range or limit of scope, interest, knowledge, etc
a thin layer of rock within a stratum that has a distinct composition, esp of fossils, by which the stratum may be dated

Etymology: 14th Century: from Latin, from Greek horizōn kuklos limiting circle, from horizein to limit, from horos limit

'horizon' also found in these entries (note: many are not synonyms or translations):

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