axis

1 of 2

noun

ax·​is ˈak-səs 

plural axes ˈak-ˌsēz 

1

a

: 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

6

a

: 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

Axis

2 of 2

adjective

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

Synonyms

Noun

• base
• capital
• center
• central
• core
• cynosure
• epicenter
• eye
• focus
• ground zero
• heart
• hub
• locus
• mecca
• navel
• nerve center
• nexus
• nucleus
• omphalos
• seat

Examples of axis in a Sentence

Noun

the Earth's axis of rotation

the spin of the Earth on its axis

Recent Examples on the Web

Noun

Iran retained a pivotal role in setting the axis’s strategic direction. —Renad Mansour, Foreign Affairs, 13 Nov. 2024

These extra axes of rotation allow the knee to bend with a more anatomically correct gliding motion. —Jothy Rosenberg, Forbes, 29 Oct. 2024

Adjective

The story details are still minimal outside of what’s been shown in trailers and short previews, but the game will once again see Dr. Jones chasing a relic desired by the Axis powers in the 1930s. —George Yang, Rolling Stone, 30 Oct. 2024

The agency, among its many worries, feared that the Axis powers were at work on biological weapons that would use rats as vectors. —Elizabeth Kolbert, The New Yorker, 30 Sep. 2024

Word History

Etymology

Noun

Middle English, "imaginary line passing through the center of a body, celestial axis," borrowed from Latin, "axletree, axle, chariot, celestial axis," going back to Indo-European *h₂eḱs- "axle," whence also, with varying thematic derivation, Germanic *ahsō (whence Old English eax "axle," Old Saxon & Old High German ahsa), Old Russian/Eastern Church Slavic osĭ "axle," Bosnian-Croatian-Serbian ôs, Lithuanian ašìs, Old Prussian assis, Greek axon-, áxōn, Sanskrit ákṣaḥ, Avestan aša- "armpit"

Note: The Indo-European base *h₂eḱs- also has derivatives with a suffixal l, for which see ala, axletree; compare also Welsh echel "axle, pivot," Breton ahel, which may go back to *akselā. The various thematic forms and extensions of h₂eḱs- may reflect a root noun rather than an i-stem as in Latin; see E. Hamp, "Refining Indo-European Lexical Entries," Zeitschrift für vergleichende Sprachforschung, 95. Band, 1. Heft (1981), pp. 81-83. The original meaning of the noun may have been "shoulder joint"—if so, Avestan would be the only language to preserve this sense. It has been suggested that *h₂eḱs- was formed by a "root extension" -s- from the verbal base *h₂eǵ- "drive (cattle, etc.), set in motion (see agent).

First Known Use

Noun

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

Adjective

1938, in the meaning defined above

Phrases Containing axis

• axis deer
• major axis
• minor axis
• optic axis
• semimajor axis
• semiminor axis
• x-axis
• y-axis
• z-axis

Kids Definition

axis

noun

ax·​is ˈak-səs 

plural axes ˈak-ˌsēz 

1

a

: 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

called also axis of symmetry

c

: one of the reference lines of a coordinate system

2

a

: a bodily structure around which parts are arranged in a symmetrical way

b

: the main stem of a plant from which leaves and branches arise

Medical Definition

axis

noun

ax·​is ˈak-səs 

plural axes -ˌsēz 

1

a

: 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

2

a

: 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