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. In World War II, Germany, Japan and Italy were known as the Axis Powers. More recently, George W. Bush referred to Iraq, Iran, and North Korean as an Axis of Evil.

Primary Meanings of axis

a straight line through a body or figure that satisfies certain conditions
a group of countries in special alliance
Full Definitions of axis

n a straight line through a body or figure that satisfies certain conditions

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coordinate axis
one of the fixed reference lines of a coordinate system
major axis
the longest axis of an ellipse or ellipsoid; passes through the two foci
semimajor axis
one-half the major axis of an ellipse; the distance from the center of an ellipse to one end
minor axis
the shorter or shortest axis of an ellipse or ellipsoid
semiminor axis
one-half the minor axis of an ellipse
optic axis, principal axis
a line that passes through the center of curvature of a lens so that light is neither reflected nor refracted
optic axis
in a doubly refracting crystal, the line in the direction of which no double refraction occurs
the horizontal axis in a plane coordinate system
the vertical axis in a plane coordinate system
the third axis in a 3-dimensional coordinate system
Type of:
a spatial location defined by a real or imaginary unidimensional extent

n the center around which something rotates

axis of rotation
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pin, pivot
axis consisting of a short shaft that supports something that turns
rotor head, rotor shaft
the axis around which the major rotor of a helicopter turns
the pivot about which a lever turns
a pin or bolt forming the pivot of a hinge
Type of:
device consisting of a piece of machinery; has moving parts that perform some function

n the main stem or central part about which plant organs or plant parts such as branches are arranged

axis of a compound leaf or compound inflorescence
the fleshy axis of a spike often surrounded by a spathe
Type of:
stalk, stem
a slender or elongated structure that supports a plant or fungus or a plant part or plant organ

n the 2nd cervical vertebra; serves as a pivot for turning the head

axis vertebra
Type of:
cervical vertebra, neck bone
one of 7 vertebrae in the human spine located in the neck region

n a group of countries in special alliance

scheduled territories, sterling area, sterling bloc
the group of countries whose currencies are tied to the British pound sterling
Type of:
alignment, alinement, alliance, coalition
an organization of people (or countries) involved in a pact or treaty

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