Geometry
Geometry is so much more than learning the names of shapes for young children. When we think of Geometry, we might harken back to that high school class where we had to memorize loads of formulas to determine circumference, area, diameters, and volume. This is NOT what we do with young children.
For young children, geometry is really housed in a larger concept that we call “spatial thinking.” This includes mathematical skills such as categorizing shapes and objects, measurement, perspective, mental transformation of shapes (being able to turn a shape upside down), scaling, proportion,and location. This list is in no way complete, as there are many more ways that spatial thinking can be taught and learned in the early years.
An examination of the physical environment is one sure-fire way to get kids talking about geometry. Using examples from the area around you and them, try to look for shapes, edges, lengths, and areas.
Copying shapes using manipulatives such as tangrams is another way to explore geometry. We are going to look broadly at tangrams another day, but for now, take a look at these two sets of tangrams and consider how children can explore them. 
I do remember memorizing a lot of things in regards to geometry when I was in school especially High School. As I think of the younger children it is so true that that is not the way we teach them geometry. Great input.
The concept of “spatial thinking” is important to teach to children because this helps children think mathematically while having fun.