A point has no size, but marks itself in space.

• It is represented by a small dot, and it is labeled with a capital letter.

A line extends in opposite directions without end. It has no width, and it cannot be measured.

• It is represented by a straight line with an arrow on each end, and it is labeled using the names of two points on the line. It can also be labeled with one lowercase cursive letter.

A flat surface that extends out in all directions. It is represented by a flattened rectangle shape. A place cannot be measured.

• It is labeled with 3 points that are not in a straight line.  A plane can also be labeled with a capital script letter written in a corner.

Space is the air around us. It is the place where everything exists. Space cannot be measured.  

• There is no specific notation for space.

Line Segment

A line segment has length, but no width. It it considered to be part of a line between two  points. The distance between the two points is considered the legth of the line segment.

• A line is named with the two endpoints and a line over them. The lenght of the line is notated using just the two endpoints.

A ray has no length and is sometimes thought of as half of a line. It has one endpoint and continues in one direction endlessly.

• A ray is named using the endpoint first and another point that the ray passes through.

The set of points two or more geometric figures have in common.

• If two figures have just one point in common, then that point is called the point of intersetion.

A pair of angles that share a vertex and a side.

* The term adjacent means "side by side."

Angles whose measures add up to 90 degrees.

* These angles make a right angle.

Angles that add up to 180 degrees.

A Linear pair is created by two angles that are adjacent and supplementary.

A polygon where the line connecting any two points inside the polygon lies wholly inside the polygon.

A polygon where the line connecting any two points inside the polygon will go outside of the polygon.

* Concave polygon "caves in" at some point.

Polygons: Triangle; Quadrilateral; Pentagon; Hexagon; Heptagon; Octagon; Nonagon; Decagon or Decahedron; Dodecagon; n-gon.

• Triangle - 3 sides
• Quadrilateral - 4 sides
• Pentagon - 5 sides
• Hexagon - 6 sides
• Heptagon - 7 sides
• Octagon - 8 sides
• Nonagon - 9 sides
• Decagon or Decahedron - 10 sides
• Dodecagon - 12 sides
• N-gon - "n" sides

All of the sides have equal length and all of the interior angles have equal measure.

The vertices* of a polygon are the points on the corners where two line segments come togehter.

* Plural form of "vertex"

The distance from the center of the polygon to the vertex.

The distance from the center of a regular polygon to the midpoint of the side of the polygon.

* It must also be perpendicular to the side of the polygon.

All three sides of the triangles are equal lengths.

None of the sides are the same length.

All three angles are the same size.

One angle measures 90 degrees.

A quadrilateral with 2 pairs of adjacent sides congruent.

The set of points in a plane that are equidistant from one point.

A congruence statement is a statement about different sides, angles, or figures that are congruent.

 * Example: Triangle ABC is congruent or equal to Triangle DEF.