Download Geometry VOCABULARY

Geometry VOCABULARY
Angles
Obtuse angle- angle that is larger than 90˚
Right angle- angle that is 90˚ (can use corner of paper to measure perfectly up and down)
Acute angle- angle that is less than 90˚ (it’s small, “cute”)
Straight angle- angle that measures 180˚ (like a straight line)
Zero angle- angle that measures 0˚ (the arms are on top of each other)
2-D shapes
Polygon- means many sides, figure that has 3 or more sides
Quadrilateral- quad- means four, ANY 4 sided figure
Rectangle- a 4 sided figure with 4 right angles
Square- 4 sided figure with 4 congruent sides and 4 right angles
Scalene triangle- triangle whose sides are all of different lengths
Isosceles triangle- triangle with 2 congruent sides
Equilateral triangle- all three sides of the triangle are congruent
Parallelogram- a quadrilateral with both pairs of opposite sides parallel
Equilateral- a figure that has all sides congruent
Rhombus- quadrilateral with 4 congruent sides
Trapezoid- quadrilateral with 1 pair of parallel sides
Pentagon- pent- means 5, any 5-sided figure
Hexagon- hex- means 6, 6-sided figure
Octagon- oct- means 8, any 8-sided figure
3-D shapes
Prism- a 3 D figure with 2 congruent bases that each have 3 or more sides.
Cube- a 3D figure whose 6 faces are all squares
Pyramid- a 3D figure with a base that has 3 or more sides and triangular faces that meet at a point
Cone- a 3D figure with a circular base and a curved surface that slopes to a vertex
Cylinder- - a 3D figure with 2 congruent circular bases
Rectangular prism- a 3D figure whose 6 faces are all rectangles
Sphere- a 3D figure that every point of the figure is the same distance from a point called the
center
Attributes
Perpendicular lines- lines that intersect to form right angles (90˚)
Parallel lines- two or more lines that are always the same distance apart and will never intersect
Line of symmetry/Reflective symmetry- a line that divides a figure into two mirror images
Rotational symmetry- when a figure can be turned less than 360˚ and be identical (same)
Face- a flat surface of a 3D figure
Edge- the intersection of 2 faces
Vertex (1)/vertices (more than 1)- the intersection of edges
Transformations
Reflection- a flip of a geometric figure
Rotation- a turn of a geometric figure
Translation- a slide of a geometric figure
Contraction- a transformation that decreases the size of the geometric figure without changing its
shape
Expansion- a transformation that increases the size of the geometric figure without changing its
shape
Net- a 2D (flat) figure that can be cut and folded to form a 3D (raised) figure