Geometry Honors - Vocab Unit 1

Point

Basic building block of geometry

no size

identifies a location usually with coordinates

Notation: single Capital Letter

Line

Straight continuous arrangement consisting of minimum 2 points

No maximum

Has direction, Length (2D)

Notation: 2 Capital letters and a line w/ 2 arrows over; One cursive lowercase letter

Plane

Length and Width can exist infinitely in all directions

No thickness

Made up of at least 3 points (not on the same line)

Notation: Capital Letter in corner of drawn plane; 3 non-collinear points indicated by the letter and/or actual point on that plane)

Collinear

When all points are on the same line

Non-Collinear

NOT on the same line

Line Segment

Consists of a start point, A, and an end point, B, and all points between those points

Notation: 2 Capital Letters and a line segment over the letters (NO ARROWS)

Ray

Line with a distinct side points and continues in one direction forever

Notation: 2 Capital Letters and a ray above them (Start point = First letter for a ray)

Opposite Rays

A point that two rays share, but go opposite lengths (If point B is between points A and C, then BA and BC are opposite rays)

Distance

How far 2 points are (The distance between points A and B is the absolute value of the difference between their points/coordinates)

Segment Addition Postulate

If B is between A and C, then AB + AC = AC (between ≠ middle, between = collinear)

Midpoint

A point that divides the segment into 2 congruent pieces - exactly in the middle

Bisector

To cut a line in half; shown by tik/hash marks that indicated congruent pieces

Straight Angles

Opposite rays are two rays that are part of the same line and have only their endpoints in common

Figure makes a straight line, or 180 degrees

Angles

Made from a vertex and 2 sides (each ray is referred to as a “side”)

Notation: Three Capital Letters that represent each ray/vertex with an angle symbol at the front

Vertex

Common point

Adjacent Angles

2 angles right next to each other that share a common ray and vertex, do NOT share any common interior points/overlap

Linear Pairs

Are formed if and only if they’re adjacent and their non common sides are opposite rays/straight angles

Complimentary

If and only if their sum is 90 degrees

Supplementary

If and only if their sum is 180 degrees

Angle bisector

A common ray within an angle that divides the angle into 2 CONGRUENT angles

Vertical angles

2 angles are vertical if and only if they’re non adjacent angles formed by a pair of intersecting lines (ARE CONGRUENT)

Angle Addition Postulate

If B lies on the interior of angle AOC, then angle AOB + angle BOC = angle AOC

Side of polygon

Each segment that forms a polygon

Diagonal

A segment that connects 2 non consecutive vertices together

Equilateral

Equal side lengths

Equilangular

Equal interior angle measures

Concave

A minimum of one diagonal that lies outside the polygon

Convex

When all diagonals lie inside the polygon