Geometric Terms starting with O-P

Geometric terms can sometimes fluster a K-6 student.  Some can sound so familiar from use, and some they can barely pronounce!  Use this easy to follow geometry dictionary and have all the geometry terms they need explained.

This resource, online is entirely free.  However, if you would like to have a physical copy at home, off-line, for your student to have easy access to, please consider purchasing the e-book - Kindergarten to Sixth Grade Geometry Dictionary.

For just $5.95 - it is excellent value!

Geometric Terms starting with O-P

Oblique: Lines at an angle to the x-axis

Oblique Prism: A prism with bases not aligned directly above one another.

Obtuse Angle: Any angle greater than 90 degrees and less than 180 degrees.

Obtuse Triangle: A triangle with one obtuse angle.

Octa: Prefix for 8

Octagon: An eight sided polygon.

Octahedron: A polyhedron with 8 faces

Order of rotation: How many times an outline matches its original during one full rotation.

Ordered Pair: Where information is given through a pair of numbers and the order is critical.  Ordered pairs are used in coordinate geometry to indicate a points position.  (1,3) is not the same as (3,1)

Origin: The point of intersection of the X-axis and Y-axis on the Cartesian plane.

Parallel lines: Lines that will never intersect.

Parallelogram: A quadrilateral with opposite sides equal in length and parallel.

Pattern: A repetition of objects.

Pentagon: A 5 sided polygon.

Pentahedron: A Polyhedron with 5. 

Perimeter: The outline of a two dimensional shape.

Perpendicular: Two lines that meet at 90 degrees are said to be perpendicular.

Perpendicular Bisector: A line that meets a line segment at 90 degrees AND bisects it.

Pi: The ratio of a circles circumference to its diameter.

Plane Shape: A flat shape with only two dimensions.

Platonic Solid: Five Regular Polyhedra made only with either equilateral triangles, squares or pentagons.

Poly: Prefix for MANY.

Polygon: A plane shape with three or more straight sides.

Polyhedron: Three dimensional objects made with plane shapes.

Position: Where something is when compared to an object or its surroundings.

Prism: Right Prism: A three dimensional shape made of two identical plane shapes, and all other faces are rectangles; Oblique Prism: Made of two identical plane shapes, and all other faces are parallelograms.

Protractor: An instrument used in geometric construction to measure degrees of angles.

Pyramid: A three dimensional shape with a polygon as its base and all other faces congruent triangles that meet at the top (its vertex).

Pythagoras: A Greek mathematician who lived circa 500 BC. Famous for his theorem on Right Angled Triangles.

Pythagorean Theorem: In a right angled triangle, the square of the hypotenuse is equal to the sum of the squares of the other two sides.

If you searched this page for a geometry definition and did not find it - please contact me.
With your help, I can make this the best resource online for parents tutoring their children in basic geometry.

Enjoy this page? Please pay it forward. Here's how...

Would you prefer to share this page with others by linking to it?

  1. Click on the HTML link code below.
  2. Copy and paste it, adding a note of your own, into your blog, a Web page, forums, a blog comment, your Facebook account, or anywhere that someone would find this page valuable.

I am sure you will find all the information and worksheets you need here, however if there is anything you cannot find please don't hesitate to contact me or simply visit the MathMomentumCommunity and join the conversation!

I love to hear from my readers, and with a little feedback and a few suggestions I can make this a great resource for parents, teachers and tutors alike.

Be sure to explore everything on this site starting at the home page.