# Geometry Vocab - Points, Lines, Angles, & Polygons

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### Point

A location represented by a dot

### Line

An infinate set of points extending endlessly in both directions

### Plane

Set of points that form a flat surface that extends infinitely in both directions

### Collinear

Points that are on the same line

### Non-collinear

Points that are not on the same line

### Betweenness

B is between A and C if and only if A, B, C are distinct collinear points and AB + BC = AC

### Coplanar

Points that are on the same plane

### Parallel Lines

2 lines that never intersect (in same plane)

### Perpendicular Lines

2 lines that intersect to form right angles (in same plane)

### Line segment

Set of points consisting of two points on a line, called endpoints , and all points on the line between the endpoints

### Length/Measure of a Segment

Distance between its endpoints

### Congruent Segments

Segments that have the same length/measure

### Midpoint

Point on a segment that divides the segments into 2 congruent segments

### Bisector of a Segment

Line, ray or a segment that intersects a segment at its midpoint

### Ray

Part of a line consisting of an endpoint and extending infinitely in the other direction

### Opposite Rays

2 rays of the SAME LINE with a common endpoint.

### Angle

The union of 2 rays having the same endpoint (vertex)

### Straight Angle

A 180 degree angle (line)

### Acute Angle

Between 0 degrees and 90 degrees

### Right Angle

A 90 degree angle

### Obtuse Angle

between 90 degrees and 180 degrees

### Congruent Angles

Two angles that have the same measure

### Angle Bisector

Ray whose endpoint is the vertex of the angle and it divides the angle into 2 congruent angles

### Complementary Angles

A pair of angles, the sum of whose degree measures 90 degrees

### Supplementary Angles

A pair of angles, the sum of whose degree measures 180

### Linear Pair

2 adjacent angles whose sum is a straight angle

### Vertical Angles

Angles formed across from one another and are congruent

Two angles who share a common vertex, common side (ray), but no common interior points

### Polygon

A closed figure in a plane that is the union of line segments such that the segments only intersect at their endpoints and no segments sharing a common endpoint are collinear.

### Triangle

A polygon that has exactly 3 sides

### Scalene triangle

Triangle that has exactly had no cogruent sides

### Isosceles Triangle

Triangle that has 2 congruent sides

### Equilateral Triangle

Triangle that has 3 congruent sides

### Acute Triangle

Triangle that has 3 acute angles

### Equiangular Triangle

Triangle that has 3 congruent angles

### Right Triangle

Triangle that has a right angle

### Obtuse Triangle

Triangle that has an obtuse angle

### Parallel Lines

Lines in the same plane that have no points in common OR all points in common.

### Altitude

(height) Line segment drawn from a vertex to the opposite side and is perpendicular to it.

### Median

Line segment drawn from a vertex to the midpoint of the opposite side.

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