Number line - American Education
A horizontal line divided into equal units beginning from a central point marked zero and extending in either direction toward a theoretical infinity. The number line is a commonly used pedagogical tool for graphic depiction of the relationships of positive and negative numbers. Units to the right of zero are marked +1, +2, +3 and so on, representing positive numbers, while those to the left are marked –1, –2, –3, representing negative numbers. In addition to positive and negative numbers, the number line offers a graphic method for teaching basic arithmetic concepts such as addition, subtraction, multiplication and division.