Geometry Words
In short: Geometry words explained: 87 terms on shapes, angles, lines, area, volume, congruence, and transformations, each defined in plain language with a short example you can sketch while reviewing for a test.
Vertex, ray, parallel, perpendicular, polygon, radius, surface area, congruent, reflection: these geometry words appear in every grade, and each one has an exact meaning. This page defines them in a sentence and describes a small figure for each, so you can picture the idea and draw it on scratch paper.
Use it when a worksheet asks you to “name the adjacent angles” or “find the lateral area” and you are unsure which part of a figure is meant. Before a test, print the pages, cover the definitions, and sketch each term from memory. Checking your drawing against the entry shows quickly what you have mastered.
87 words on this page, each with a definition, a figure, a solved example and two quick questions.
Geometry Words: the full list
6th Grade
- Area
- Area of a Parallelogram
- Area of a Trapezoid
- Area of a Triangle
- Coordinate Plane
- Net (3D Figure)
- Ordered Pair
- Quadrants
- Rectangular Prism
- Surface Area
- Volume
7th Grade
- Adjacent Angles
- Area of a Circle
- Circumference
- Complementary Angles
- Cross Section
- Pi (π)
- Radius and Diameter
- Scale Drawing
- Scale Factor
- Supplementary Angles
- Triangle Inequality Theorem
- Vertical Angles
8th Grade
- Alternate Interior Angles
- Congruent Figures
- Corresponding Angles
- Dilation
- Distance Formula
- Exterior Angle Theorem
- Hypotenuse
- Pythagorean Theorem
- Pythagorean Triple
- Reflection (Geometry)
- Rotation (Geometry)
- Similar Figures
- Translation (Geometry)
- Transversal
- Triangle Angle Sum Theorem
- Volume of a Cone
- Volume of a Cylinder
- Volume of a Sphere
Geometry
- AA Similarity
- Angle
- Angle Bisector
- Arc (Circle)
- Arc Length
- Area of a Sector
- Cavalieri's Principle
- Central Angle
- Centroid
- Chord
- Circumcenter
- Conditional Statement
- Congruent Triangles
- Converse
- CPCTC
- Equation of a Circle
- Focus and Directrix
- HL Theorem (Hypotenuse-Leg)
- Incenter
- Inscribed Angle
- Isosceles Triangle Theorem
- Line Segment
- Midpoint Formula
- Midsegment of a Triangle
- Parallel Lines
- Parallelogram
- Perpendicular Bisector
- Perpendicular Lines
- Point, Line and Plane
- Ray
- Rhombus
- Rigid Transformation
- Same-Side Interior Angles
- Similar Triangles
- Solid of Revolution
- Tangent to a Circle
- Triangle Congruence (SSS, SAS, ASA, AAS)
- Two-Column Proof
- Volume of a Pyramid