Hydrogen is by far the most abundant element in the universe. It makes up about 93 percent of all atoms in the universe and about three-quarters of the total mass of the universe. Hydrogen occurs both within stars and in the interstellar space (the space between stars).
It is an imaginary line from the Earth's north pole to its south pole, passing through the center of the Earth. Imaginary in the sense that it is not marked in any way; howeve â¦ r, Earth rotates around this axis.
LINK / CITE ADD TO WORD LIST. noun. The definition of an axis is a real or imaginary line on which something rotates, or a straight line around which things are evenly arranged. 1  An example of axis is an imaginary line running through the earth on which the earth rotates.