ax·​is | \ˈak-səs \
plural axes\ -​ˌsēz \

Definition of axis 

(Entry 1 of 2)

1a : a straight line about which a body or a geometric figure rotates or may be supposed to rotate the Earth's axis

b : a straight line with respect to which a body or figure is symmetrical the axis of a cone

called also axis of symmetry

c : a straight line that bisects at right angles a system of parallel chords of a curve and divides the curve into two symmetrical parts

d : one of the reference lines of a coordinate system (see coordinate entry 3 sense 1a)

2 anatomy

a : the second vertebra of the neck on which the head and first vertebra turn as on a pivot

b : any of various central, fundamental, or axial parts

3 botany : a plant stem

4 crystallography : one of several imaginary lines assumed in describing the positions of the planes by which a crystal is bounded and the positions of atoms in the structure of the crystal

5 : a main line of direction, motion, growth, or extension the axis of a city

6a : an implied line in painting or sculpture through a composition to which elements in the composition are referred fruit and flowers arranged about a diagonal axis

b : a line actually drawn and used as the basis of measurements in an architectural or other working drawing

7 aviation : any of three fixed lines of reference in an aircraft that run in the longitudinal, lateral, and vertical directions, are mutually perpendicular, and usually pass through the aircraft's center of gravity

8 : partnership, alliance an axis of countries

9 : a point or continuum on which something centers an axis of social power



Definition of Axis (Entry 2 of 2)

: of or relating to the three powers Germany, Italy, and Japan engaged against the Allied nations in World War II

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Examples of axis in a Sentence


the Earth's axis of rotation the spin of the Earth on its axis

Recent Examples on the Web: Noun

Instead, the Houses reflect the earth’s own 24-hour rotation around its axis. Aliza Kelly Faragher, Allure, "The 12 Astrological Houses: Interpreting Your Birth Chart Beyond the Zodiac," 6 Oct. 2018 The rocket was not designed to survive an in-flight escape and was slammed with 70,000 pounds of off-axis force and hot exhaust. Eric Berger, Ars Technica, "Blue Origin to subject its rocket to high-altitude escape test," 18 July 2018 This works because the North Star is almost directly in line with the Earth's axis of rotation. Rhett Allain, WIRED, "Figure Out Where You Are With Nothing But a Watch and Protractor," 3 May 2018 Like our sun rises and sets as the Earth spins on its axis, so do the stars in the sky. Brian Resnick, Vox, "Summer is for meteor showers and stargazing. Here’s how to watch.," 22 June 2018 The reason the summer solstice is the longest day of the year is because the tilt of Earth's axis is most inclined toward the sun, making the sun's highest point of elevation between June 20 and June 22 every year. Alessandra Rincón, Billboard, "Google Doodle Celebrates the Summer Solstice," 21 June 2018 For example, the solutions to x5 = 1 are five points on a circle when plotted onto a graph comprised of real numbers along one axis and imaginary numbers on the other. Davide Castelvecchi, Scientific American, "“Grand Unified Theory of Math” Nets Abel Prize," 20 Mar. 2018 Along the axis, a high-energy jet of particles sent photons and neutrinos racing in our direction at or near the speed of light. Smithsonian, "Scientists Explain The Thrill of Detecting a Neutrino From a Far-Off Galaxy," 12 July 2018 However, the Earth's axis of rotation is tilted 23.5 degrees to the plane of its orbit around the sun. Tom Skilling,, "Ask Tom: Has there ever been a sunrise not followed by a sunset?," 29 June 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'axis.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of axis


14th century, in the meaning defined at sense 1a


1938, in the meaning defined above

History and Etymology for axis


Latin, axis, axle; akin to Old English eax axis, axle, Greek axōn, Lithuanian ašis, Sanskrit akṣaḥ

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Statistics for axis

Last Updated

16 Nov 2018

Look-up Popularity

Time Traveler for axis

The first known use of axis was in the 14th century

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More Definitions for axis



English Language Learners Definition of axis

: the imaginary straight line that something (such as the Earth) turns around

: a straight line that divides a shape evenly into two parts


ax·​is | \ˈak-səs \
plural axes\ ˈak-​ˌsēz \

Kids Definition of axis

1 : a straight line about which a body or a geometric figure rotates or may be thought of as rotating the earth's axis

2 : a line of reference used to assign numbers to locations in a geometric plane


ax·​is | \ˈak-səs \
plural axes\ -​ˌsēz \

Medical Definition of axis 

1a : a straight line about which a body or a geometric figure rotates or may be thought of as rotating

b : a straight line with respect to which a body, organ, or figure is symmetrical

2a : the second vertebra of the neck of the higher vertebrates that is prolonged anteriorly within the foramen of the first vertebra and united with the dens which serves as a pivot for the atlas and head to turn upon

called also epistropheus

b : any of various central, fundamental, or axial parts the cerebrospinal axis the skeletal axis

c : axilla

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Comments on axis

What made you want to look up axis? Please tell us where you read or heard it (including the quote, if possible).


by force of circumstances

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