40 terms

# 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.