It is OFTEN the x axis, but not always. Sometimes it is the t-axis (for time). In basic economics it could be quantity (q), in Demographics it could be age (y, for years). There are many alternatives.
x axis
For the same reason the we read left to right horizontally. It is a natural motion of the eyes and head and hand. They started that way and found no reason to change. The bigger question is why do they read right to left, when writing is always going to smudge the ink.
They write left to right if they write horizontally. When writing vertically they would write from right to left.
Ancient Egyptian hieroglyphics can be written both vertically and horizontally. When written vertically, it is from top to bottom. When written horizontally, it can be both from left to right, or right to left. When reading hieroglyphs, you will need to pay attention to the facing of the hieroglyphic alphabet. Any faces, people or animals in the hieroglyphic alphabet will face the start of the sentence. For example, in the hieroglyph for the 'a' sound, if the eagle faces the left, then the sentence should be read from left to right.
The right for all women across the nation to have the right to vote.
Be always sure you're right - Then go ahead
The X axis.
On a standard Cartesian graph, there are two axes. The Y axis runs vertically, bottom to top and the X axis runs horizontally from left to right.
X Axis
A horizontal line is a line that goes across (left to right or right to left).
Written on a line across the page but centered on the page
Yes because you need the data on the right and across the bottom to make the graph
downward as they proceed from left to right across a graph
Generally the x-axis is displayed on a 2-dimensional Cartesian Coordinate system running horizontally (left to right - for negative to positive values of x) In a 3-D graph, the x-axis is usually shown running diagonally from upper right to lower left (for negative to positive values of x) . In a 3-D graph, the y-axis is the one running horizontally and the z-axis is vertical.
There are many graphs which while you can usually use most of them no matter what experiment you are doing that is not always true, nor is it the right use of a graph. some of the most likely graphs you will probably come across , or for that matter need to use are bar graphs, line graphs, pie graphs, and picture graphs.
Planets appear to move horizontally when they are in that part of the ecliptic that lies horizontally across the southern horizon at midnight (seen from the northern hemisphere). That occurs when a planet is at a right-ascension of 18 hours (in Sagittarius), and a couple of hours either side. A snapshot of the planet taken every night at midnight shows it moving horizontally (approximately) from right to left. All planets do this.
left to right --------------------------------
g(x) = √(x - 16) The graph of g(x) = √(x - 16) has the same shape as the graph of f(x) = √x. However, it is shifted horizontally to the right 16 units. The graph of the function f(x)=square root(x) is made up of half a parabola (in the first quadrant) with directrix (16, 0), which opens rightward. The domain is [16,∞) and range [0, ∞).