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Geometric Jargon
cube
octagon
Slide
Acute Angle
An angle with a measure less than 90
“What a-cute angle!”
Angle
Two rays that share an endpoint
Area
The measure, in square units, of the inside
region of the 2-dimensional figure
Base of a Solid Figure
A special face of a solid figure
Chord
A line segment that joins
any two points on a circle
Chord AB
A
B
Circle
A closed curve with all its points in one plane
and the same distance from the center
Circle
Circumference
The perimeter of a circle
Cone
A 3-dimensional figure with 1 curved
surface, 1 flat surface (usually circular),
1 curved edge, and 1 vertex
cone
Compass
A tool used to draw circles
Congruent
Having exactly the same size and shape
Coordinate Grid
A two-dimensional system in which the
coordinates of a point are its distances
from two intersecting perpendicular lines
called axes
y
Coordina e
x
Coordinates
An ordered pair of numbers that gives the
location of a point on a coordinate grid
Cube
A regular solid with 6 congruent square faces
Square face
Cylinder
A 3-dimensional figure with 2 parallel and
congruent circles as bases, 1 curved
surface, 2 curved edges, and 0 vertices
base
curved
surface
edges
Diagonal
A line segment that joins two vertices of a
polygon but is not a side of the polygon
Diameter
A chord that goes through the center of a circle
Edge
The line segment where two faces of a solid
figure meet
Edge
Equilateral Triangle
A triangle with all sides the same length
Face
A plane figure that serves as one side of a
solid figure
face
Height
The length of a perpendicular line segment
from a vertex to the base
height
Hexagon
A polygon with 6 sides
Hexagon
Intersecting Lines
Lines that meet or cross at a common point
in ersec ing lines
Isosceles Triangle
A triangle that has two congruent sides
Congruent
Sides
Kite
A quadrilateral with two pairs of adjacent
congruent sides
Length
The distance along a line
or figure from one point
to another
LENGTH
Line
An infinite set of points forming a straight
path that goes in two directions without
end
Line Segment
A part of a line defined by two endpoints
Line of Symmetry
A line that divides a figure into
two congruent halves that are
mirror images of each other
Net
A 2-dimensional shape that can be folded
into a 3-dimensional figure is a net of that
figure
NE
net of a cube
Obtuse Angle
An angle with a measure greater than 90º
and less than 180º
Parallel Lines (l l)
Lines that never intersect (always the same
distance apart)
Parallelogram
A quadrilateral with two pairs of parallel and
congruent sides
Pentagon
A polygon with 5 sides
Perimeter
The distance around a figure
Perpendicular lines
Lines that intersect to form right angles
Plane
A flat surface that extends infinitely in all
directions
Polygon
A closed plane figure formed from line
segments that meet only at their endpoints
Prism
A 3-dimensional figure that has two
congruent and parallel faces that are
polygons. The rest of the faces are
parallelograms.
Pyramid
A polyhedron whose base is a polygon and
whose other faces are triangles that share
a common vertex
Quadrilateral
A polygon with 4 sides
Radius
The segment, or the length of the segment,
from the center of the circle to any point
on the circle
Ray
A part of a line that has one endpoint and
extends indefinitely in one direction
Rectangle
A quadrilateral with two pairs of congruent,
parallel sides and four right angles
Rectangular Prism
A prism with 6 rectangular faces
Reflection (flip)
A transformation creating a mirror image of
a figure on the opposite side of a line
Rhombus
A parallelogram with all 4 sides equal in
length
Right Angle
An angle that measures exactly 90º
Rotation (turn)
A transformation in which a figure is turned
a given angle and direction around a point
Scalene Triangle
A triangle that has no congruent sides
Similar Figures
Figures that have the same shape, but not
necessarily the same size
Sphere
A 3-dimensional figure made up of all points
that are equally distant from a point called
the center
Square
A parallelogram with 4 congruent sides and
4 right angles
Square Pyramid
A pyramid with a square base
Straight Angle
An angle with a measure of 180º
Tessellation
A covering of a plane without overlaps or
gaps using combinations of congruent
figures
Three-Dimensional
An object that has length, width, and height
Translation (slide)
A transformation that slides a figure a given
distance in a given direction
Trapezoid
A quadrilateral with exactly two parallel lines
Triangle
A polygon with three angles and three sides
(“tri” means 3)
Triangular Pyramid
A pyramid with a base that is a triangle
Two-Dimensional
A figure that has length and width, but not
height
Vertex
The point at which two line segments, lines,
or rays meet to form an angle. Also, a
point on a polyhedron where three or more
faces intersect.
Volume
The number of cubic units it takes to
fill a solid
Volume = 12
cubic units
Width
One dimension of a 2- or 3- dimensional figure
width