3Rd Grade Geometry

Front 1

line

Back 1

a straight path that goes on forever in opposite directions

Front 2

line segment

Back 2

part of a line, a line segment has two endpoints

Front 3

ray

Back 3

a part of a line that has one endpoint and goes on forever in one direction

Front 4

angle

Back 4

a figure formed by two rays with the same endpoint

Front 5

right angle

Back 5

an angle that measures 90 degrees

Front 6

parallel lines

Back 6

lines that do not intersect

Front 7

intersecting lines

Back 7

lines that cross each other

Front 8

perpendicular lines

Back 8

lines that intersect at right angles

Front 9

plane figure

Back 9

a geometric figure that has two dimensions

Front 10

polygon

Back 10

a simple, closed plane figure made up of three or more line segments

Front 11

side

Back 11

a line segment that is part of a polygon

Front 12

vertex (vertices)

Back 12

a point common to two sides of a polygon or the edges of a solid figure

Front 13

regular polygon

Back 13

a polygon with sides all the same length and angles the same size

Front 14

irregular polygon

Back 14

a polygon with sides of different lengths and angles that may be of different sizes

Front 15

equilateral triangle

Back 15

a triangle that has three congruent sides

Front 16

isosceles triangles

Back 16

a triangle that has two congruent sides

Front 17

right triangle

Back 17

a triangle with one right angle

Front 18

scalene triangle

Back 18

a triangle with sides of all different lengths

Front 19

quadrilateral

Back 19

a polygon with four sides

Front 20

parallelogram

Back 20

a quadrilateral whose opposite sides are equal

Front 21

rectangle

Back 21

a quadrilateral with four right angles

Front 22

square

Back 22

a rectangle with four equal sides and four right angles

Front 23

diagonal

Back 23

a line segment connecting two vertices of a polygon that are not next to each other

Front 24

solid figures

Back 24

figures that have three dimensions

Front 25

rectangular prism

Back 25

a solid figure whose faces are all rectangular

Front 26

cube

Back 26

a solid figure that has six square faces of equal size

Front 27

sphere

Back 27

a solid figure that is shaped like a round ball

Front 28

cone

Back 28

a solid figure with one circular face and one curved surface

Front 29

cylinder

Back 29

a solid figure with two congruent, circular faces and one curved surface

Front 30

pyramid

Back 30

a solid figure whose base is a polygon and whose other faces are triangles with a common vertex

Front 31

face

Back 31

a flat surface of a solid figure

Front 32

edge

Back 32

the line segment where the faces of a solid figure meet

Front 33

congruent

Back 33

figures that have the same size and shape

Front 34

similar

Back 34

having the same shape, but not necessarily the same size

Front 35

symmetry

Back 35

a figure has symmetry if it can be folded along a line so that the two parts match exactly

Front 36

line of symmetry

Back 36

the line on which a figure can be folded so that the two halves match exactly

Front 37

flip

Back 37

to turn something over, front to back

Front 38

slide

Back 38

moving a figure along a line

Front 39

turn

Back 39

to rotate a figure around a point

Front 40

perimeter

Back 40

the distance around a figure

Front 41

area

Back 41

the number of square units in a region

Front 42

volume

Back 42

the number of cubic units that fit inside a solid figure

Front 43

cubic unit

Back 43

a cube used to measure volume, each edge is equal to a unit of measure