The Basics
Euclid described this fundamental geometric idea as "that which has no part," having location but no size.
What is a point?
The part of a line bounded by two distinct endpoints, allowing its length to be measured.
What is a line segment?
This common geometric tool is used specifically to measure the degrees of an angle.
What is a protractor?
A flat, closed 2D shape formed entirely by three or more straight line segments.
What is a polygon?
The proper geometric notation used to write out "line segment AB"
What is a bar over AB with no arrows)?
This geometric entity has no beginning or endpoint, extends forever in two opposite directions, and cannot be measured.
What is a line?
This figure starts at a single endpoint and extends infinitely in only one direction.
What is a ray?
The shared endpoint where two rays meet to form an angle.
What is a vertex?
The general mathematical term for any polygon that has exactly four sides.
What is a quadrilateral?
If a test question asks you to find the total distance around the outside edge of a polygon, you are calculating this specific metric.
What is the perimeter?
This flat surface has no boundaries, thickness, or edges, and extends infinitely in all directions.
What is a plane?
The specific point that divides a line segment exactly into two congruent pieces.
What is a midpoint?
An angle whose measurement sits strictly between 0 degrees and 90 degrees.
What is an acute angle?
A polygon featuring five sides and five vertices.
What is a pentagon?
The the math textbook Euclid wrote.
Who is "The Elements?"
This term describes three or more points that lie along the exact same straight line.
What is collinear?
A term in geometry that means to cut a segment or an angle into exactly two equal halves.
What is to bisect?
An angle that measures greater than 90 degrees but less than 180 degrees.
What is an obtuse angle?
A polygon that has eight sides and eight angles.
What is an octagon?
Angles that measure 180 degrees.
What are straight angles?
Points or lines that sit completely within the same geometric plane.
What is coplanar?
Two geometric line segments are given this title if they possess the exact same length.
What are congruent segments?
A figure made with only a compass and straight edge.
What is a construction?
A 3D figure bounded entirely by flat polygon surfaces that exists in space.
What is a polyhedron?
The area formula for a rectangle.
What is A = lh