acute angle An angle with a measure less than that of a right angle. Houghton Mifflin Co. 2 Grade 5 Unit 6

acute angle An angle with a measure less than that of a right angle. Houghton Mifflin Co. 2 Grade 5 Unit 6

angle An angle is formed by two rays with a common end point. Houghton Mifflin Co. 3 Grade 5 Unit 6

area The number of square units that cover a surface with no overlap. Houghton Mifflin Co. 4 Grade 5 Unit 6

base of a geometric figure base base A bottom side or face of a geometric figure. Houghton Mifflin Co. 8 Grade 5 Unit 6

center (of a circle) center A point that is the same distance from all points on a circle. Houghton Mifflin Co. 10 Grade 5 Unit 6

central angle central angle An angle with a vertex at the center of a circle. Houghton Mifflin Co. 12 Grade 5 Unit 6

chord chords Any segment within a circle that connects two points on the circle. Houghton Mifflin Co. 14 Grade 5 Unit 6

circle A closed figure in which every point is the same distance from a given point called the center of the circle. Houghton Mifflin Co. 15 Grade 5 Unit 6

circumference The distance around a circle. Houghton Mifflin Co. 17 Grade 5 Unit 6

cone A solid that has a circular base and a surface from a boundary of the base to the vertex. Houghton Mifflin Co. 27 Grade 5 Unit 6

congruent Figures having the same size and shape. Houghton Mifflin Co. 28 Grade 5 Unit 6

cube A solid figure that has six square faces of equal size. Houghton Mifflin Co. 32 Grade 5 Unit 6

cubic unit A cube with all edges one unit long. Houghton Mifflin Co. 33 Grade 5 Unit 6

cylinder A solid with two circular faces that are congruent and a cylindrical surface connecting the two faces. Houghton Mifflin Co. 34 Grade 5 Unit 6

degree A unit used to describe angle measures. Its symbol is. Houghton Mifflin Co. 39 Grade 5 Unit 6

diagonal E A D AC and BE are diagonals for the pentagon. B C A segment that joins two vertices of a polygon but is not a side. Houghton Mifflin Co. 40 Grade 5 Unit 6

diameter (of a circle) diameter A segment that connects two points on the circle and passes through the center. Houghton Mifflin Co. 41 Grade 5 Unit 6

edge edge The segment where two faces of a solid figure meet. Houghton Mifflin Co. 47 Grade 5 Unit 6

equilateral triangle A triangle that has three congruent sides. Houghton Mifflin Co. 50 Grade 5 Unit 6

irregular polygon A polygon with at least one side or angle that is not congruent to the others. Houghton Mifflin Co. 78 Grade 5 Unit 6

isosceles triangle 5 cm 5 cm A triangle that has at least two congruent sides. Houghton Mifflin Co. 79 Grade 5 Unit 6

line symmetry The line along which a figure can be folded so that that the two halves match exactly. Houghton Mifflin Co. 84 Grade 5 Unit 6

net A flat pattern that can be folded to make a solid figure. Houghton Mifflin Co. 94 Grade 5 Unit 6

obtuse angle An angle with a measure greater than that of a right angle and less than 180. Houghton Mifflin Co. 95 Grade 5 Unit 6

pentagonal prism A solid figure that has pentagons for bases and parallelograms for faces. Houghton Mifflin Co. 103 Grade 5 Unit 6

pentagonal pyramid A solid figure whose base is a pentagon and whose faces are triangles. Houghton Mifflin Co. 104 Grade 5 Unit 6

perimeter The distance around a plane figure. Houghton Mifflin Co. 107 Grade 5 Unit 6

pi ( ) A number defined by the ratio of the circumference of any circle to its diameter. Two common approximations used for pi are 2 2 and 3.14. 7 Houghton Mifflin Co. 109 Grade 5 Unit 6

polygon A simple closed plane figure made up of three or more line segments. Houghton Mifflin Co. 111 Grade 5 Unit 6

prism A solid figure that has two parallel congruent bases and parallelograms for faces. Houghton Mifflin Co. 118 Grade 5 Unit 6

pyramid A solid figure whose base can be any polygon and whose faces are triangles. Houghton Mifflin Co. 122 Grade 5 Unit 6

quadrilateral A polygon with four sides. Houghton Mifflin Co. 124 Grade 5 Unit 6

radius radius A segment that connects the center of a circle to any point on the circle. Houghton Mifflin Co. 126 Grade 5 Unit 6

rectangular prism A solid figure with six faces that are rectangles. Houghton Mifflin Co. 132 Grade 5 Unit 6

reflection A transformation that flips a figure over a line. Houghton Mifflin Co. 133 Grade 5 Units 6, 8

regular polygon A polygon with all sides congruent and all angles congruent. Houghton Mifflin Co. 134 Grade 5 Unit 6

right angle An angle that measures 90. Houghton Mifflin Co. 137 Grade 5 Unit 6

rotation A transformation that turns a figure about a given point. Houghton Mifflin Co. 138 Grade 5 Units 6, 8

rotational symmetry If a figure can be turned less than a full turn about a given point and the figure looks exactly the way it did before the turn, that figure has rotational symmetry. Houghton Mifflin Co. 139 Grade 5 Units 6, 8

scalene triangle A triangle with no congruent sides. Houghton Mifflin Co. 143 Grade 5 Unit 6

solid figure A three-dimensional figure in space. Houghton Mifflin Co. 147 Grade 5 Unit 6

sphere A solid figure that is shaped like a round ball. Houghton Mifflin Co. 149 Grade 5 Unit 6

square pyramid A solid figure with a square for a base and triangles for faces. Houghton Mifflin Co. 151 Grade 5 Unit 6

square unit A square with sides one unit long. Houghton Mifflin Co. 152 Grade 5 Unit 6

straight angle 180 An angle that measures 180. Houghton Mifflin Co. 156 Grade 5 Unit 6

surface area The total area of the surface of a solid. Houghton Mifflin Co. 158 Grade 5 Unit 6

symmetric figure A figure that has line or rotational symmetry. Houghton Mifflin Co. 160 Grade 5 Unit 6

tessellation A repeating pattern that covers a plane without gaps or overlaps. Houghton Mifflin Co. 162 Grade 5 Unit 6

transformation A transformation changes the position of a plane figure. Some transformations are rotations, translations, and reflections. Houghton Mifflin Co. 164 Grade 5 Units 6, 8

translation A transformation that slides a figure a given distance in a given direction. Houghton Mifflin Co. 165 Grade 5 Units 6, 8

triangular prism A prism whose bases are triangles. Houghton Mifflin Co. 167 Grade 5 Unit 6

triangular pyramid A pyramid whose base is a triangle. Houghton Mifflin Co. 168 Grade 5 Unit 6

vertex (vertices) vertex vertex A point common to the two sides of an angle. Houghton Mifflin Co. 173 Grade 5 Unit 6

volume The number of cubic units that make up a solid figure. Houghton Mifflin Co. 174 Grade 5 Unit 6