Quadrilateral just means “four sides”
A Quadrilateral has four-sides, it is 2-dimensional (a flat shape), closed (the lines join up), and has straight sides.
Try drawing a quadrilateral, and measure the angles. They should add to 360°
There are special types of quadrilateral:
Some types are also included in the definition of other types! For example a square, rhombus and rectangle are also parallelograms.
You can find if a shape has a Line of Symmetry by folding it.
When the folded part sits perfectly on top (all edges matching), then the fold line is a Line of Symmetry.
Here I have folded a rectangle one way, and it didn’t work.
So this is not a Line of Symmetry
But when I try it this way, it does work (the folded part sits perfectly on top, all edges matching):
So this is a Line of Symmetry