| A | B |
|---|
| point | an exact location in space |
| line | a set of points that goes on forever in two directions |
| line segment | part of a line having two endpoints |
| midpoint | the point half-way between the endpoints of a line segment |
| ray | part of a line that has one endpoint and extends forever in only one direction |
| plane | an endless flat surface |
| parallel lines | in a plane, lines that never cross and are the same distance apart |
| intersecting lines | lines that pass through the same point |
| perpendicular lines | two lines that intersect to form right angles |
| angle | two rays that have the same endpoint |
| vertex of an angle | the common endpoint in an angle |
| sides of an angle | the two rays that form the angle. (Note: the length of the sides does not change the size of the angle.) |
| interior of an angle | the points between the two rays that form an angle |
| exterior of an angle | the points outside the rays that form an angle |
| degrees | a unit of measure for angles |
| protractor | an instrument used to measure and draw angles |
| acute angle | an angle whose measure is less than 90 degrees. |
| right angle | an angle whose measure is exactly 90 degrees |
| obtuse angle | an angle whose measure is larger than 90 degrees |
| straight angle | an angle whose measure is exactly 180 degrees making it a straight line |
| circle | a closed plane figure made up of all the points the same distance from one point called the center |
| center | the point from which all points in a circle are equally distant |
| radius | any line segment that connects the center of a circle to a point on the circle |
| diameter | any line segment through the center that connects two points on the circle. |
| chord | a line segment that connects two points on the circle |
| central angle | an angle whose vertex is the center of the circle |
| polygon | a closed figure made up of line segments |
| triangle | a polygon with 3 sides and three angles that add up to 180 degrees |
| quadrilateral | a polygon with four sides and four angles that add up to 360 degrees |
| pentagon | a polygon with five sides and five angles that add up to 540 degrees. |
| hexagon | a polygon with six sides and six angles that add up to 720 degrees |
| octagon | a polygon with eight sides and eight angles that add up to 1,080 degrees |
| regular polygon | a polygon which has sides of equal length and angles of equal measure |
| equilateral triangle | a triangle whose sides all have the same length and angles all have the same measure |
| isosceles triangle | a triangle with at least two sides of the same length |
| scalene triangle | a triangle in which no sides have the same length |
| right triangle | a triangle in which one angle is a right angle |
| acute triangle | a triangle whose angles are all acute angles (angles less than 90 degrees) |
| obtuse triangle | a triangle in which one angle is an obtuse angle. (greater than 90 degrees) |
| parallelogram | a quadrilateral (four sided figure) with both pairs of opposite sides parallel and no 90 degree angles |
| trapezoid | a quadrilateral (four sided figure) that has only one pair of parallel sides |
| rectangle | a parallelogram with four right angles; a quadrilateral (four sided figure) with both pairs of opposite sides parallel and equal in length and all 90 degree angles |
| rhombus | a parallelogram with all sides the same length; a quadrilateral (four sided figure) with all sides parallel and equal in length and no 90 degree angles |
| square | a rectangle with all sides the same length; a quadrilateral (four sided figure) with both pairs of all sides parallel and equal in length and all right angles |
| similar figures | figures that have the same shape. They may or may not have the same size. |
| congruent figures | figures that have the same size and shape |
| transformations | a move such as a slide, flip, or turn that does not change the size or shape of a figure |
| slide (translation) | slide (transformation) the change in the position of a figure that moves it up, down, or sideways |
| flip (reflection) | the change in the position of a figure that gives the mirror image of the figure |
| turn (rotation) | the change in the position of a figure that moves it around a point |
| symmetric figure | a figure that can be folded into two congruent parts that fit on top of each other |
| line of symmetry | the fold line in a symmetric figure |
