A scale is a series of marks at regular intervals along a line, used for measuring. A scale usually uses a number line. There are a number of different uses of the term "scale."
The scales on thermometers and rulers have numbered lines.
The term "scale" is also used as the name of a tool for measuring weight.
In a picture graph, the graph scale is the ratio between the picture or icon and the number it represents. In contrast, in a bar graph or line graph, the graph scale is the ratio between each space on the graph and the number it represents.
The scale for this picture graph is: 1 spaceship = 6 students
The scale for this bar graph is: 1 square = hour.