Points, Lines, and Shapes! Geometry Points, Lines, and Shapes!

Plane plane A flat surface that stretches into infinity.

Point point A location in a plane or in space, having no dimensions.

Line Segment line segment Two points on a line, and all the points between those two points.

Line line A straight set of points that extends into infinity in both directions.

Ray ray part of a line, with one endpoint, and extending to infinity in one direction.

Intersecting Lines intersecting lines Lines that have one and only one point in common.

Parallel Lines parallel lines Two lines are parallel if they are in the same plane and never intersect.

Perpendicular Lines perpendicular lines Two lines are perpendicular if the angle between them is 90 degrees.

Angle angle The union of two rays with a common endpoint, called the vertex.

Acute Angle acute angle A positive angle measuring less than 90 degrees.

Right Angle right angle An angle whose measure is 90 degrees.

Obtuse Angle obtuse angle An angle whose measure is greater than 90 degrees.

Straight Angle straight angle An angle that measures 180 degrees.

Polygon polygon A closed plane figure made up of several line segments that are joined together.

Triangle triangle A three-sided polygon. Triangles can be classified according to the measures of their angles and their sides.

Acute Triangle acute triangle A triangle each of whose angles measures less than 90 degrees.

Right Triangle right triangle A triangle that contains a right angle.

Obtuse Triangle obtuse triangle A triangle with an obtuse angle.

Scalene Triangle scalene triangle A triangle with no congruent (exactly the same size and shape) sides.

Isosceles Triangle isosceles triangle A triangle with two congruent (exactly the same size and shape) sides.

Equilateral Triangle equilateral triangle A triangle with all sides that are congruent (exactly the same size and shape).

Circle circle The set of points in a plane that are a fixed distance from a given point, called the center.

Circle circle The set of points in a plane that are a fixed distance from a given point, called the center.

Quadrilateral quadrilateral Any four-sided figure is called a quadrilateral.

Parallelogram parallelogram A quadrilateral with opposite sides parallel.

Rectangle rectangle A parallelogram with four 90-degree (right) angles.

Square square A parallelogram with four congruent (equal) sides and four 90 degree (right) angles.

Rhombus rhombus A parallelogram with four congruent (equal) sides. Opposite angles are congruent.

Trapezoid trapezoid A quadrilateral that has exactly one pair of parallel sides. The parallel sides are called bases. The non-parallel sides are called legs. If the legs have the same length, then the trapezoid is an isosceles trapezoid. Isosceles Trapezoid Isosceles Trapezoid

Kite kite A quadrilateral that is shaped like a diamond. Sometimes people like to fly them!  It has two distinct pairs of adjacent (side-by-side) congruent sides.

Cylinder cylinder a solid figure that has two parallel bases that are congruent circles

Cone cone a solid figure that has a flat, circular base and one vertex

Cube cube a solid figure with six congruent square faces

Square Pyramid Square Pyramid a solid figure with a square base and with four triangular faces that have a common point

Rectangular Prism Rectangular Prism a solid figure in which all six faces are rectangles.

Rotation (turn) Rotation (turn) a movement of a figure to a new position by turning it around a vertex

Reflection (flip) Reflection (flip) a movement of a figure to a new position by flipping it over a line

Translation (slide) Translation (slide) a movement of a figure to a new position along a straight line