# Number Line

In basic mathematics, a number line is a picture of a straight line on which every point is assumed to correspond to a real number and every real number to a point. Often the integers are shown as specially-marked points evenly spaced on the line. Although this image only shows the integers from −9 to 9, the line includes all real numbers, continuing forever in each direction, and also numbers not marked that are between the integers. It is often used as an aid in teaching simple addition and subtraction, especially involving negative numbers.

It is divided into two symmetric halves by the origin, i.e. the number zero.

In advanced mathematics, the expressions real number line, or real line are typically used to indicate the above-mentioned concept that every point on a straight line corresponds to a single real number, and vice versa.

### Other articles related to "number line, line, lines, numbers":

Cartesian Coordinate System - Definitions - Number Line
... a one-dimensional space—that is, for a straight line—means choosing a point O of the line (the origin), a unit of length, and an orientation for the line ... An orientation chooses which of the two half-lines determined by O is the positive, and which is negative we then say that the line "is oriented" (or "points") from the negative half towards the positive ... Then each point p of the line can be specified by its distance from O, taken with a + or − sign depending on which half-line contains p ...
Hatch Mark - Unit and Value Marks
... Every ruler or number line that uses vertical line segments to mark distance values is using unit value hatch marks ... The marks appear as single vertical line segments that are parallel to each other and evenly spaced ... For example, longer line segments are usually used for integers (or just natural numbers) ...
Coord - Number Line
... The simplest example of a coordinate system is the identification of points on a line with real numbers using the number line ... In this system, an arbitrary point O (the origin) is chosen on a given line ... the distance taken as positive or negative depending on which side of the line P lies ...
Drawing The Number Line
... The number line is usually represented as being horizontal ... Customarily, positive numbers lie on the right side of zero, and negative numbers lie on the left side of zero ... on either end of the drawing is meant to suggest that the line continues indefinitely in the positive and negative real numbers, denoted by ...
Point At Infinity
... infinity, also called ideal point, of the real number line is a point which, when added to the number line yields a closed curve called the real projective line ... The real projective line is not equivalent to the extended real number line, which has two different points at infinity ... complex algebraic curve) known as the complex projective line, also called the Riemann sphere ...

### Famous quotes containing the words line and/or number:

The line that I am urging as today’s conventional wisdom is not a denial of consciousness. It is often called, with more reason, a repudiation of mind. It is indeed a repudiation of mind as a second substance, over and above body. It can be described less harshly as an identification of mind with some of the faculties, states, and activities of the body. Mental states and events are a special subclass of the states and events of the human or animal body.
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The quality of moral behaviour varies in inverse ratio to the number of human beings involved.
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