Plane Geometry
If you like drawing, Geometry is for you!
Plane geometry is all about shapes like lines, circles and triangles ... shapes that can be drawn on a flat surface called a Plane (it is like on an endless piece of paper). 
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)
Hint: Try drawing some of the shapes and angles as you learn ... it helps.
Shapes
Polygons
A Polygon is a 2dimensional shape made of straight lines. Triangles and Rectangles are polygons.
Here are some more:
Properties of Regular Polygons  
Diagonals of Polygons  
Interactive Polygons 
The Circle
Circle  
Pi  
Circle Sector and Segment  
Circle Area by Sectors  
Annulus  
(Advanced) Circle Theorems  
Symbols
There are many special symbols used in Geometry. Here is a short reference for you: 
Congruent and Similar
Congruent Shapes  
Similar Shapes 
Angles
Using Drafting ToolsUsing the Protractor 
Transformations and Symmetry 

Activity: Symmetry of Shapes Activity: Make a Mandala Activity: Coloring (The Four Color Theorem) 

Tessellations Tessellation Artist 
Coordinates 

Cartesian Coordinates  
Interactive Cartesian Coordinates  
Hit the Coordinate Game  
More Advanced Topics in Plane Geometry
Pythagoras 

Conic Sections 

Set of all points  
Conic Sections  
Ellipse  
Parabola  
Hyperbola  
TrigonometryTrigonometry is a special subject of its own, so you might like to visit: 