Key takeaway: Geometry terms name shapes, measurements and relationships in the plane and in space, from area and volume to transversals, congruent triangles, chords and ellipses.
Geometry has the largest vocabulary of any topic in school math, because every shape, angle pair and theorem has a name. These geometry terms run from the area formulas of Grade 6 to the proofs of high school Geometry and the vectors and conic sections of Precalculus.
Every page includes a labeled figure, which is often the fastest way to understand a geometry definition.
87 terms on this page, each with a definition, a figure and a worked example.
Geometry Terms: the full list
Grade 6
- Area 6.G.A.1
- Area of a Parallelogram 6.G.A.1
- Area of a Trapezoid 6.G.A.1
- Area of a Triangle 6.G.A.1
- Coordinate Plane 6.NS.C.6b
- Net (3D Figure) 6.G.A.4
- Ordered Pair 6.NS.C.6c
- Quadrants 6.NS.C.6b
- Rectangular Prism 6.G.A.2
- Surface Area 6.G.A.4
- Volume 6.G.A.2
Grade 7
- Adjacent Angles 7.G.B.5
- Area of a Circle 7.G.B.4
- Circumference 7.G.B.4
- Complementary Angles 7.G.B.5
- Cross Section 7.G.A.3
- Pi (π) 7.G.B.4
- Radius and Diameter 7.G.B.4
- Scale Drawing 7.G.A.1
- Scale Factor 7.G.A.1
- Supplementary Angles 7.G.B.5
- Triangle Inequality Theorem 7.G.A.2
- Vertical Angles 7.G.B.5
Grade 8
- Alternate Interior Angles 8.G.A.5
- Congruent Figures 8.G.A.2
- Corresponding Angles 8.G.A.5
- Dilation 8.G.A.3
- Distance Formula 8.G.B.8
- Exterior Angle Theorem 8.G.A.5
- Hypotenuse 8.G.B.6
- Pythagorean Theorem 8.G.B.7
- Pythagorean Triple 8.G.B.7
- Reflection (Geometry) 8.G.A.1
- Rotation (Geometry) 8.G.A.1
- Similar Figures 8.G.A.4
- Translation (Geometry) 8.G.A.1
- Transversal 8.G.A.5
- Triangle Angle Sum Theorem 8.G.A.5
- Volume of a Cone 8.G.C.9
- Volume of a Cylinder 8.G.C.9
- Volume of a Sphere 8.G.C.9
Grade 10 – Geometry
- AA Similarity G-SRT.A.3
- Angle G-CO.A.1
- Angle Bisector G-CO.D.12
- Arc (Circle) G-C.A.2
- Arc Length G-C.B.5
- Area of a Sector G-C.B.5
- Cavalieri's Principle G-GMD.A.1
- Central Angle G-C.A.2
- Centroid G-CO.C.10
- Chord G-C.A.2
- Circumcenter G-C.A.3
- Conditional Statement G-CO.C.9
- Congruent Triangles G-CO.B.7
- Converse G-CO.C.9
- CPCTC G-CO.B.7
- Equation of a Circle G-GPE.A.1
- Focus and Directrix G-GPE.A.2
- HL Theorem (Hypotenuse-Leg) G-SRT.B.5
- Incenter G-C.A.3
- Inscribed Angle G-C.A.2
- Isosceles Triangle Theorem G-CO.C.10
- Line Segment G-CO.A.1
- Midpoint Formula G-GPE.B.6
- Midsegment of a Triangle G-CO.C.10
- Parallel Lines G-CO.C.9
- Parallelogram G-CO.C.11
- Perpendicular Bisector G-CO.C.9
- Perpendicular Lines G-GPE.B.5
- Point, Line and Plane G-CO.A.1
- Ray G-CO.A.1
- Rhombus G-CO.C.11
- Rigid Transformation G-CO.A.5
- Same-Side Interior Angles G-CO.C.9
- Similar Triangles G-SRT.B.5
- Solid of Revolution G-GMD.B.4
- Tangent to a Circle G-C.A.4
- Triangle Congruence (SSS, SAS, ASA, AAS) G-CO.B.8
- Two-Column Proof G-CO.C.9
- Volume of a Pyramid G-GMD.A.3
Grade 12 – Precalculus
- Conic Sections G-GPE.A.3
- Dot Product N-VM.B.5
- Ellipse G-GPE.A.3
- Hyperbola G-GPE.A.3
- Magnitude of a Vector N-VM.A.1
- Polar Coordinates N-CN.B.4
- Vector N-VM.A.1