# Step 2 Unit 5 Key Terms

• 2-Dimensional: A shape that only has two dimensions (such as width and height) and no thickness or depth.
• 3-Dimensional: An object that has height, width, and depth (thickness), like any object in the real world.
• Area: The number of square units it takes to completely fill a space or surface.
• Bases of a Prism: The two faces formed by congruent polygons that lie in parallel planes, all of the other faces being parallelograms.
• Cubic Units: Volume of the solids is measured in Cubic Units.
• Edge: The intersection of a pair of faces in a three-dimensional figure.
• Equilateral Triangle: A triangle which has all three of its sides equal in length.
• Face: One of the polygons that makes up a polyhedron.
• Fractional edge length: The length of each edge of the cube is a fraction.
• Isosceles Triangle: A triangle which has two of its sides equal in length.
• Kite: A quadrilateral with two distinct pairs of equal adjacent sides. A kite-shaped figure.
• Lateral Faces:   In a prism, a face that is not a base of the figure.
• Net: A two-dimensional figure that, when folded, forms the surfaces of a three-dimensional object.
• Parallelogram: A quadrilateral with both pairs of opposite sides parallel.
• Polygon: A number of coplanar line segments, each connected end to end to form a closed shape.   A regular polygon has all sides equal and all interior angles equal.   An irregular polygon’s sides are not all the same length nor do the interior angles have the same measure.
• Polyhedron: A 3-dimensional figure that has polygons as faces.
• Prism: A polyhedron with two parallel and congruent faces, called bases, and all other faces that are parallelograms.
• Quadrilaterals: Four coplanar line segments linked end to end to create a closed figure. A 4-sided polygon.
• Rectangle:   A 4-sided polygon where all interior angles are 90°.
• Rectangular prism: A solid (3-dimensional) object which has six faces that are rectangles.
• Rhombus: A quadrilateral with all four sides equal in length.
• Right Triangle: A triangle where one of its interior angles is a right angle (90 degrees).
• Right rectangular prism:  In a right prism, the lateral faces are each perpendicular to the bases.
• Scalene Triangle: A triangle where all three sides are different in length.
• Square: A quadrilateral that has four right angles and four equal sides.
• Surface area: The total area of the 2-dimensional surfaces that make up a 3-dimensional object, measured in units squared.
• Trapezoid: A quadrilateral which has one pair of parallel sides.
• Triangles: A closed figure consisting of three line segments linked end-to-end. A 3-sided polygon.
• Triangular prism: A prism whose bases are triangles.   A solid 3-dimensional object that has five faces: three rectangles and two bases.
• Vertices: The common endpoint of two or more rays or line segments
• Volume: The amount of space occupied by an object, measured in units cubed.

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