Geometry
Geometry is all about shapes and their properties.
If you like playing with objects, or like drawing, then geometry is for you!
Geometry can be divided into:
Plane Geometry is about flat shapes like lines, circles and triangles ... shapes that can be drawn on a piece of paper
Solid Geometry is about three dimensional objects like cubes, prisms, cylinders and spheres.
Hint: Try drawing some of the shapes and angles as you learn ... it helps. 
Point, Line, Plane and Solid
A Point has no dimensions, only position
A Line is onedimensional
A Plane is two dimensional (2D)
A Solid is threedimensional (3D)
Why?
Why do we do Geometry? To discover patterns, find areas, volumes, lengths and angles, and better understand the world around us.
Plane Geometry
Plane Geometry is all about shapes on a flat surface (like on an endless piece of paper).
 Quadrilaterals (Rhombus, Parallelogram, etc)
 Rectangle, Rhombus, Square, Parallelogram, Trapezoid and Kite
 Interactive Quadrilaterals
 Parallelogram In Any Quadrilateral
 Paper Sizes
 Shapes Freeplay
Polygons
A Polygon is a 2dimensional shape made of straight lines. Triangles and Rectangles are polygons.
Here are some more:
The Circle
 Circle
 Pi
 Circle Area by Lines
 Circle Sector and Segment
 Circle Area by Sectors
 Activity: Dropping a Coin onto a Grid
 Arc
 Annulus
Circle Theorems (Advanced Topic)
Symbols
There are many special symbols used in Geometry. Here is a short reference for you:
Congruent and Similar
Angles


Using Drafting Tools
 Geometric Constructions
 Using the Protractor
 Using the Drafting Triangle and Ruler
 Using a Ruler and Compass
Transformations and Symmetry
Coordinates
More Advanced Topics in Plane Geometry
Pythagoras
Conic Sections
Circle Theorems
 Circle Theorems
 Tangent and Secant Lines
 Intersecting Secants Theorem
 Intersecting Chords Theorem
 Angle of Intersecting Secants Theorem
Trigonometry
Trigonometry is a special subject of its own, so you might like to visit:
Solid Geometry
Solid Geometry is the geometry of threedimensional space  the kind of space we live in ...
... let us start with some of the simplest shapes:
Polyhedra and NonPolyhedra
There are two main types of solids, "Polyhedra", and "NonPolyhedra":
Polyhedra (they must have flat faces):
Cubes and Cuboids (Volume of a Cuboid) 

Platonic Solids  
Prisms  
Pyramids 
NonPolyhedra (when any surface is not flat):
Sphere  Torus  
Cylinder  Cone 
 Polyhedron Models
 Volume and Area of a Sphere Calculator
 Spheroid
 Cross Sections
 Vertices, Faces, and Edges
 Cone vs Sphere vs Cylinder
 Pyramid vs Cone
 Prism vs Cylinder
 Pyramid vs Cube
 Volume of Horizontal Cylinder
 Euler's Theorem
 Pythagoras in 3D
 Hypercubes
 Builder's Math
 Moments of Area