What is Graph?
[[Image:Us unemployment rates 1950 2005.png|thumb|right|This graph shows the [[unemployment rate]] by year in the [[United States]].]] A '''graph''' is a picture designed to express words, particularly the [[connection]] between two or more quantities. You can see a graph on the right. A simple graph usually shows the relationship between two numbers or measurements in the form of a [[grid]]. If this is a ''rectangular graph'' using [[Cartesian coordinate system]], the two measurements will be arranged into two different lines at [[right angle]] to one another. One of these lines will be going up (the ''vertical'' [[Axis (mathematicsr)|axis]]). The other one will be going right (the ''horizontal'' axis). These lines (or ''axes'', the [[plural]] of axis) meet at their ends in the lower left corner of the graph. Both of these axes have ''tick marks'' along their lengths. You can think of each axis as a [[ruler]] drawn on paper. So each measurement is indicated by the length of the associated tick mark along the particular axis. A graph is a kind of [[chart]] or [[diagram]]. However, a chart or a diagram may not relate one quantity to other quantities. ''[[Flowchart]]s'' and ''tree diagrams'' are charts or diagrams that are not graphs. __TOC__ == How to draw a simple graph == Let's say you wanted to make a graph showing your height as you were growing up. You might show your height in [[centimeters]] on the vertical axis and your age in years on the horizontal axis. For example, say you were 60 centimeters tall at age 1, 85 centimeters tall at age 2 and 95 centimeters tall at age 3. You would draw an imaginary straight line passing through the 50 centimeters height mark on the vertical axis. Then you would draw a second imaginary line passing through the age of 1 year on the horizontal axis. At the place where the two imaginary lines meet (called their ''[[intersection]]''), you would then draw a dot. Really, the imaginary lines are usually replaced by ''graph paper'' (see below). The drawing of this interse