axis

¹ American  

[ak-sis] / ˈæk sɪs /

noun

plural

axes

1. the line about which a rotating body, such as the earth, turns.

2. Mathematics.

   1. a central line that bisects a two-dimensional body or figure.

   2. a line about which a three-dimensional body or figure is symmetrical.

3. Anatomy.

   1. a central or principal structure, about which something turns or is arranged.

      the skeletal axis.

   2. the second cervical vertebra.

4. Botany. the longitudinal support on which organs or parts are arranged; the stem and root; the central line of any body.

5. Analytic Geometry. any line used as a fixed reference in conjunction with one or more other references for determining the position of a point or of a series of points forming a curve or a surface.

6. Crystallography. crystallographic axis.

7. Aeronautics. any one of three lines defining the attitude of an airplane, one being generally determined by the direction of forward motion and the other two at right angles to it and to each other.

8. Fine Arts. an imaginary line, in a given formal structure, about which a form, area, or plane is organized.

9. an alliance of two or more nations to coordinate their foreign and military policies, and to draw in with them a group of dependent or supporting powers.

10. the Axis, (in World War II) Germany, Italy, and Japan, often with Bulgaria, Hungary, and Romania.

11. a principal line of development, movement, direction, etc.

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axis ² American  

[ak-sis] / ˈæk sɪs /

noun

plural

axises

1. axis deer.

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axis ¹ British  

/ ˈæksɪs /

noun

1. a real or imaginary line about which a body, such as an aircraft, can rotate or about which an object, form, composition, or geometrical construction is symmetrical

2. one of two or three reference lines used in coordinate geometry to locate a point in a plane or in space

3. anatomy the second cervical vertebra Compare atlas

4. botany the main central part of a plant, typically consisting of the stem and root, from which secondary branches and other parts develop

5. an alliance between a number of states to coordinate their foreign policy

6. Also called: principal axis.  optics the line of symmetry of an optical system, such as the line passing through the centre of a lens

7. geology an imaginary line along the crest of an anticline or the trough of a syncline

8. crystallog one of three lines passing through the centre of a crystal and used to characterize its symmetry

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axis ² British  

/ ˈæksɪs /

noun

1. any of several S Asian deer of the genus Axis, esp A. axis. They typically have a reddish-brown white-spotted coat and slender antlers

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Axis ³ British  

/ ˈæksɪs /

noun

1. 1. the alliance of Nazi Germany, Fascist Italy, and Japan, established in 1936 and lasting until their defeat in World War II

   2. ( as modifier )

      the Axis powers

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axis Scientific  

/ ăk′sĭs /

plural

axes

1. An imaginary line around which an object rotates. In a rotating sphere, such as the Earth and other planets, the two ends of the axis are called poles. The 23.45° tilt of the Earth's axis with respect to the plane of its orbit around the Sun causes the Northern and Southern Hemispheres to point toward and away from the Sun at different times of the year, creating seasonal patterns of weather and climate. Other planets in the solar system have widely varying tilts to their axes, ranging from near 0° for Mercury to 177° for Venus.

2. Mathematics

   1. A line, ray, or line segment with respect to which a figure or object is symmetrical.

   2. A reference line from which distances or angles are measured in a coordinate system, such as the x-axis and y-axis in the Cartesian coordinate system.

3. Anatomy The second cervical vertebra, which serves as a pivot for the head.

4. Botany The main stem or central part of a plant or plant part, about which other plant parts, such as branches or leaflets, are arranged.

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axis ¹ Cultural  

1. In geometry, a straight line about which an object may rotate or that divides an object into symmetrical halves.

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axis ² Cultural  

1. An imaginary straight line passing through the North Pole, the center of the Earth, and the South Pole. The Earth rotates around this axis.

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Usage

Plural word for axis The plural form of axis is axes, pronounced [ ak-seez ]. The plurals of several other singular words that end in -sis are also formed in the same way, including hypothesis/hypotheses, analysis/analyses, and crisis/crises. A similar change is made when pluralizing appendix as appendices. Irregular plurals that are formed like axes derive directly from their original pluralization in Latin and Greek. Be careful: axes is also the plural of ax (and its alternate spelling axe), but in this case it’s pronounced [ ak-siz ]. Do you know: What is the plural of matrix?

Discover More

The axis of the Earth is an imaginary line drawn through the North Pole and the South Pole.

Other Word Forms

• axised adjective
• unaxised adjective

Etymology

Origin of axis¹

First recorded in 1350–1400; Middle English; from Latin axis “an axletree, axle, axis”; see origin at axi-

Origin of axis²

First recorded in 1595–1605; from Latin axis “a wild animal of India, perhaps the spotted deer” (Pliny)

Explanation

An axis is a straight line, sometimes seen, sometimes not, that is important in mathematics, art, science and our survival. The most famous axis is the one the earth spins around, giving us the 24-hour day. In graphs, one side is usually the "X axis" and the other the "Y axis." Axis lines are also the lines that run through spheres, like our earth, around which those spheres rotate. In a totally different area, axis is used to describe countries in an alliance. During World War II, Germany, Japan, and Italy were known as the Axis Powers.

Example Sentences

When an electric field is applied, it changes the orientation of each atom's quantization axis.

From Science Daily • Apr. 17, 2026

As my clients embark on the private journey that is therapy, in a room thoughtfully arranged to contain everything, the room itself is the reliable axis around which meaningful and deep changes can occur.

From Los Angeles Times • Apr. 16, 2026

A revised scheme might do several things at once: minimize the visual impact on the executive residence itself, decrease the addition’s height, and shrink its footprint to preserve the axis to the U.S.

From The Wall Street Journal • Apr. 10, 2026

What makes this especially frustrating from a neuroscience perspective is that the gut-brain axis is one of the most pharmacologically sensitive systems in the body.

From Slate • Mar. 22, 2026

Whenever one of the rabbits inside stood up and rested its forepaws on the upper part of the wire, the door pivoted lightly on the axis of the staple and the lower hinge.

From "Watership Down: A Novel" by Richard Adams