altitude

American  

[al-ti-tood, -tyood] / ˈæl tɪˌtud, -ˌtyud /

noun

1. the height of anything above a given planetary reference plane, especially above sea level on earth.

   Synonyms:

   elevation

2. extent or distance upward; height.

   Antonyms:

   depth

3. Astronomy. the angular distance of a heavenly body above the horizon.

4. Geometry.

   1. the perpendicular distance from the vertex of a figure to the side opposite the vertex.

   2. the line through the vertex of a figure perpendicular to the base.

5. Usually altitudes. a high place or region.

   mountain altitudes.

6. high or important position, rank, etc.

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altitude British  

/ ˈæltɪˌtjuːd /

noun

1. the vertical height of an object above some chosen level, esp above sea level; elevation

2. geometry the perpendicular distance from the vertex to the base of a geometrical figure or solid

3. Also called: elevation.  astronomy nautical the angular distance of a celestial body from the horizon measured along the vertical circle passing through the body Compare azimuth

4. surveying the angle of elevation of a point above the horizontal plane of the observer

5. (often plural) a high place or region

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altitude Scientific  

/ ăl′tĭ-to̅o̅d′ /

1. The height of an object or structure above a reference level, usually above sea level or the Earth's surface.

2. Astronomy The position of a celestial object above an observer's horizon, measured in degrees along a line between the horizon (0°) and the zenith (90°). Unlike declination and celestial latitude —the corresponding points in other celestial coordinate systems—the altitude of star or other celestial object is dependent on an observer's geographic location and changes steadily as the sky passes overhead due to the rotation of the Earth.

3. Astronomy See more at altazimuth coordinate system

4. Mathematics The perpendicular distance from the base of a geometric figure, such as a triangle, to the opposite vertex, side, or surface.

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Synonym Usage

See height.

Other Word Forms

Derived Forms

• altitudinal
  adjective
• altitudinous
  adjective

Etymology

Origin of altitude

First recorded in 1350–1400; Middle English, from Latin altitūdō; see origin at alti-, -tude

Explanation

The noun altitude refers to how high something rises: “The high altitude of the Himalayan mountain range slowed the progress of the hikers.” Whether it refers to how high a plane is flying or to the height of a landform, the word altitude is used to describe an object’s elevation above a particular reference point. Altitude is typically measured from sea level, which is the average level of the sea’s surface. Something that is far above sea level — such as Mount Everest — is said to have a high altitude. Something closer to the ground — such as a plane approaching for landing — is said to have a low altitude.

Example Sentences

Similarly, the U.S. had 360 Terminal High Altitude Area Defense systems before the war started.

From Slate • Apr. 24, 2026

What’s more, in January, the Defense Department and Lockheed announced External link a plan to quadruple the number of Terminal High Altitude Area Defense, or THAAD, interceptors, to 400 per year from 96.

From Barron's • Mar. 3, 2026

Defense Department to quadruple the annual production of Terminal High Altitude Area Defense interceptor missiles, to 400 from 96.

From MarketWatch • Jan. 29, 2026

Altitude sickness was so severe that some had to be hooked up to intravenous drips.

From The Wall Street Journal • Dec. 5, 2025

Altitude tempers the heat of the low latitudes.

From Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 5 "Clervaux" to "Cockade" by Various

Related Words

• distance
• elevation
• peak