# axis

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.

Definitions of axis
1. noun
a straight line through a body or figure that satisfies certain conditions
see moresee less
types:
show 10 types...
hide 10 types...
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
x-axis
the horizontal axis in a plane coordinate system
y-axis
the vertical axis in a plane coordinate system
z-axis
the third axis in a 3-dimensional coordinate system
type of:
line
a spatial location defined by a real or imaginary unidimensional extent
2. noun
the center around which something rotates
synonyms: axis of rotation
see moresee less
types:
show 4 types...
hide 4 types...
pin, pivot
axis consisting of a short shaft that supports something that turns
the axis around which the major rotor of a helicopter turns
fulcrum
the pivot about which a lever turns
pintle
a pin or bolt forming the pivot of a hinge
type of:
mechanism
device consisting of a piece of machinery; has moving parts that perform some function
3. noun
the main stem or central part about which plant organs or plant parts such as branches are arranged
see moresee less
types:
rachis
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
4. noun
the 2nd cervical vertebra; serves as a pivot for turning the head
synonyms: axis vertebra
see moresee less
type of:
cervical vertebra, neck bone
one of 7 vertebrae in the human spine located in the neck region
5. noun
a group of countries in special alliance
synonyms: bloc
see moresee less
types:
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
Word Family