Basic Geometric Terms

Geometry The study of the size and shape of things It is essential to recognize geometry that exists within objects for the purpose of creating solid models or multiview drawings

Angles Acute Angle Obtuse Angle Right Angle Vertex Measures less than 90° Obtuse Angle Measures more than 90° Right Angle Measures exactly 90° Vertex Point at which two lines of an angle intersect Vertex

Circle Radius Diameter Circumference Chord Distance from the center of a circle to its edge Diameter Distance across a circle through its center Circumference Distance around the edge of a circle Chord Line across a circle that does not pass at the circle’s center

Circle Has 360° Quadrant Concentric One fourth (quarter) of a circle Measures 90° Concentric Two or more circles of different sizes that share the same center point 90°

Triangles Equilateral Isosceles Scalene All three sides are of equal length and all three angles are equal Isosceles Two sides are of equal length Scalene Sides of three different lengths and angles with three different values

Triangles HYPOTENUSE Right Triangle Hypotenuse One of the angles equals 90° Hypotenuse The side of a right triangle that is opposite the 90° angle HYPOTENUSE

Quadrilaterals Square Rectangle Trapezoid Four equal sides and all angles equal 90° Rectangle Two sides equal lengths and all angles equal 90° Trapezoid Only two sides are equal length

Quadrilaterals Rhombus Rhomboid All sides are equal length and opposite angles are equal Rhomboid Opposite sides are equal length and opposite angles are equal

Regular Polygons Pentagon Hexagon Octagon Five sided polygon Six sided polygon Octagon Eight sided polygon

Regular Polygons Heptagon Nonagon Decagon Dodecagon Seven sided polygon Nonagon Nine sided polygon Decagon Ten sided polygon Dodecagon Twelve sided polygon 11

Geometric Terms Circumscribe Inscribe Process of creating a polygon that fully encloses a circle and is tangent to all of the polygons sides Inscribe Process of creating a polygon that is fully enclosed by a circle at its corners

Regular Polygons Distance across flats Distance across corners Measurement across the parallel sides of a polygon Circumscribed Distance across corners Measurement across adjacent corners of a polygon Inscribed

Geometric Terms Bisect Tangent Divide into two equal parts A line and arc, or two arcs that touch each other at one point only

Geometric Terms Parallel Perpendicular Two or more lines that are always the same distance apart Perpendicular Two lines that are at a 90° angle

Geometric Symbols Angle Triangle Radius Diameter Parallel Perpendicular Square Centerline R C L