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### 18 Cards in this Set

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 What is a line? A line is a set of continuous points that extend indefinitely in either direction. What is a plane? A plane is a flat surface that extends infinitely in all directions. What are parallel lines? Parallel lines are two lines in the same plane that do not intersect. What is a polygon? A polygon is a closed figure with three or more sides that intersect only at their endpoints. What are postulates? Postulates are generalizations in geometry that cannot be proven true. They are just accepted as true. What is a point? A point is a specific place in space. A point has no dimension. It has no length, width or depth. What is a line segment? A line segment is a part of a line with two endpoints. What is a ray? A ray has one endpoint and extends infinitely in the other direction. What are opposite rays? Opposite rays are two rays that have the same endpoint and form a straight line. What are collinear points? Collinear points lie on the same line. What are noncollinear points? Noncollinear points do not lie on the same line. What is an angle? An angle is a pair of two rays that have the same endpoint. What are theorems? Theorems are generalizations in geometry that can be proven true. What is an acute angle? An acute angle measures less than 90 degrees. What is a right angle? A right angle measures exactly 90 degrees. What is an obtuse angle? An obtuse angle measures more than 90 degrees. What is a straight angle? A straight angle measures exactly 180 degrees. What is a reflex angle? A reflex angle has a measure greater than 180 degrees and less than 360 degrees.