Lesson 1: Geometry Vocabulary

Objective: Understand the vocabulary of geometry.
Click on each of these terms to see the defintion, an illustration, and sometimes an animation. There are too many words to learn in one day. Try to remember as many as you can. We will be using these words throughout the geometry unit. After reading each definition, close the window to return to this page. Read each definition and look at the illustrations at least twice before trying the activities at the bottom of the page.

point line line segment ray
angle right angle acute angle obtuse angle
vertex parallel line perpendicular lines intersecting lines
circle circumference chord diameter
radius triangle right triangle acute triangle
obtuse triangle equilateral triangle isosceles triangle scalene triangle
polygon parallelogram quadrilateral rectangle
square trapezoid hexagon octagon
pentagon closed figure
These activities will help you learn geometry vocabulary:

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