Geometry Terms

Geometry

Study of shapes formed by points in space.

Point

Exact location in space with no dimensions.

Line

Straight path connecting two points, extending infinitely.

Plane

Flat surface extending endlessly in all directions.

Collinear

Points that lie on the same straight line.

Noncollinear

Points that do not lie on the same line.

Coordinate Plane

Formed by two intersecting number lines.

Origin

Point of intersection of x-axis and y-axis.

Quadrants

Four sections of the coordinate plane.

Ordered Pair

Coordinates describing a point's location.

X-coordinate

Distance along the x-axis from the origin.

Y-coordinate

Distance along the y-axis from the origin.

Negative Coordinates

Coordinates left or down from the origin.

X-axis

Horizontal number line in a coordinate plane.

Y-axis

Vertical number line in a coordinate plane.

Graphing Points

Plotting points based on ordered pairs.

Coordinates

Values that determine a point's position.

Right Angles

Angles formed by intersecting axes at 90 degrees.

Coordinate System

Framework for locating points in a plane.

Geometric Figures

Shapes defined by points, lines, and planes.

Negative Quadrants

Quadrants II and III contain negative coordinates.

parallel

Parallel lines are in the same plane and never intersect. They "run" straight next to each other.

intersecting lines

Intersecting lines share a common point. They cross each other somewhere.

Perpendicular lines

Perpendicular lines are lines that cross to form right angles (90 degrees).

Angle

A figure formed by two rays with a common endpoint

complementary angles

two angles whose measures add up to 90*

supplementary angles

angles are two angles whose measures add up to 180 degrees.

tri-

3

quad-

4

penta-

5

hexa-

6

hepta-

7

octa-

8

line segment

part of a line having two endpoints

polygon

a closed figure made of line segments

vertex

the common endpoint of a pair of sides

interior angle

the angle formed between two sides of a polygon that is inside the shape.

irregular polygon

a polygon with differently-sized sides and/or angles

regular polygon

a polygon with same-sized sides and angles

closed figure

a shape with no holes or openings in it

congruent

having the same size and shape

equilateral triangle

a triangle with all sides equal in length and all angles equal in measure.

isosceles triangle

a triangle with two sides equal in length and two angles equal in measure.

scalene triangle

a triangle with all sides of different lengths and all angles of different measures.

right triangle

a triangle with one angle measuring 90 degrees.

acute triangle

a triangle with all angles measuring less than 90 degrees.

obtuse triangle

a triangle with one angle measuring more than 90 degrees.

trapezoid

a four-sided quadrilateral with at least one pair of parallel sides.

parallelogram

a four-sided quadrilateral with opposite sides that are parallel and equal in length.

quadrilateral

a four-sided polygon with four edges and four vertices.

polygon

a closed figure with three or more straight sides.

rhombus

a type of parallelogram where all four sides are of equal length.

rectangle

a quadrilateral with opposite sides equal and all angles equal to 90 degrees.

square

a special type of rectangle and rhombus where all four sides are equal and all angles are 90 degrees.

line AB

ray AB

line segment AB

the length of AB

line segment AB is perpendicular to line segment XY

line segment AB is parallel to line segment XY

angle

measure of angle ABC

congruent

right angle

similar

radius

a straight line from the center of a circle to its edge

diameter

a straight line from one edge of a circle to the other that goes through the middle of the circle

chord

a line from one edge of a circle to the other. It does not have to go through the middle

radii

plural of radius