noun pl. axes ax′es (-sēz′)

1. a real or imaginary straight line on which an object rotates or is regarded as rotating the axis of a planet
2. a real or imaginary straight line around which the parts of a thing, system, etc. are symmetrically or evenly arranged or composed the axis of a picture
3. a main line of motion, development, etc.
4. an alignment between countries, groups, etc. for promoting their purposes
5. Aeron. any of the three straight lines, perpendicular to each other, passing through the center of gravity of an aircraft, namely the longitudinal axis from nose to tail, the lateral axis from side to side, and the vertical axis from above to below
6. Anat.
   1. the second cervical vertebra
   2. any of various axial or central parts
7. Bot.
   1. the main stem of a plant
   2. the central system of a cluster
8. Geom.
   1. a straight line through the center of a plane figure or solid, esp. one around which the parts are symmetrically arranged
   2. a straight line for measurement or reference, as in a graph
9. Optics
   1. a straight line through the centers of both surfaces of a lens
   2. a straight line from the object of vision to the fovea of the eye

Etymology: L, axle, axis < IE *aks- < base *aĝ- (see act) > OE eax, ON ǫxull, Gr axōn, L axilla

noun

Etymology: ModL < L