Download Polygon—a closed plane figure with 3 or more sides

Geometry Unit Vocabulary
Lines and Angles
Point
Line—
Extends forever in both directions
Line Segment—
A part of a line with 2 endpoints
Ray—
Part of a line that has one endpoint and goes on forever in one direction
Parallel Lines—
2 straight lines that never cross;
Equal distance from each other
Intersecting Lines—
2 straight lines that cross at one point
(like a street intersection)
Acute Angle—
Less than a right angle
Obtuse Angle—
Greater than a right angle
Right Angle—
A “square” angle
(a “cute” little angle)
Plane Figures
Polygon—a closed plane figure with 3 or more sides (no curved sides)
Yes
Yes
Yes
Quadrilateral—any polygon with 4 sides
NOT A POLYGON
Triangle
3-sided
polygon
Geometry Unit Vocabulary
Rectangle
4 sides; 4 right
angles; opposite
sides are equal and
parallel
Rhombus
Trapezoid
4 sides are the
same length;
opposite sides
are parallel
Pentagon
5-sided
polygon
4 sides; 2 sides
are parallel
Hexagon
6-sided
polygon
Heptagon
Octagon
7-sided
polygon
8-sided
polygon
Nonagon
9-sided
polygon
Decagon
10-sided polygon
Congruent & Similar Figures & Symmetry
Congruent Figures—
2 plane figures that are the
same size and the same shape (like twins)
Similar Figures—
2 plane figures that have the same
shape, but can be different sizes
Geometry Unit Vocabulary
Line of Symmetry—
a line that divides a
figure into two equal
parts that are mirror
images of each other
Perimeter—the distance around a figure (Add up the length of the outside sides)
Area—the space inside a shape (In 3rd grade, we will always have it shown with the
square units drawn. The students will need to count the square units inside the shape.)
Perimeter = 4 + 1 + 1 + 2 + 1 + 1 + 2 + 2 = 14 units
Area = 8 square units
Space Figures
Be able to count the faces, vertices, edges.
Sphere
Pyramid
Cube
Rectangular Prism
Cylinder
Cone