# Defining and Constructing Objects

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## Point

A point is a geometric object that cannot be constructed using simpler objects. Meaning, it is an *undefined term*, as opposed to a *defined term*. Instead, it has to be described using its characteristics. One possible description is that a point is an object with no size, indicating a location in space. It is represented graphically with a dot.

## Line

A **line**, just like a point, is an undefined term. It is a one-dimensional object of infinite length with no width or height that never bends or turns. Its graphical representation is a straight line with arrowheads on either end, indicating that it continues indefinitely in both directions.

## Line Segment

The line segment $\overline{AB},$ or segment $\overline{AB}$, consists of the *endpoints* $A$ and $B,$ and every point on line $\overleftrightarrow{AB}$ located between $A$ and $B.$ Notice that, a segment, unlike a line, does not extend infinitely — it is bound by its endpoints.

## Plane

A plane is similar in its definition to a line, though it is two-dimensional. That is, it has an infinite width and length, but no height. It is represented by what could be seen as a floor or a wall, extending without end.

## Ray

A **ray** is a portion of a line, starting at an endpoint and extending indefinitely. The notation for a ray starts with the endpoint and another point on the ray, with an arrow drawn above it. For example, the ray below would be represented by: $\overrightarrow{AB}.$

## Exercises

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