Geometry - 2D Shapes and their Properties

2D Shapes (Two-Dimensional Shapes): These are flat figures that have only two dimensions—length and width. They do not have any thickness. Visually, think of a drawing on a flat sheet of paper or a shadow on a wall.

Sides and Vertices: The straight lines that form the boundary of a shape are called sides. The point where two sides meet is called a vertex (plural: vertices). For example, a square looks like a box with $4$ straight line segments and $4$ sharp corners where those lines connect.

Square: A square is a closed shape with $4$ sides of equal length and $4$ vertices. Visually, it is perfectly symmetrical, looking like a dice face or a floor tile, where every side is the same size.

Rectangle: A rectangle has $4$ sides and $4$ vertices. Its opposite sides are equal in length. Visually, it looks like a stretched square, resembling a mobile phone screen or a door, where the top and bottom are longer than the sides (or vice-versa).

Triangle: A triangle is a shape with $3$ sides and $3$ vertices. Visually, it can look like a mountain peak, a slice of pizza, or a 'yield' traffic sign. The sides can be equal or different in length.

Circle: A circle is a perfectly round 2D shape. It has no straight sides and no vertices. It is formed by a single curved line that is always the same distance from the center point, resembling a coin, a clock face, or a wheel.

Closed and Open Figures: A closed figure starts and ends at the same point, leaving no gaps (like a complete loop or a drawn box). An open figure has a starting point and an ending point that do not meet, looking like a 'C' shape or a wavy line with ends hanging loose.

Quadrilaterals: Any flat shape with $4$ straight sides is called a quadrilateral. This group includes squares and rectangles. Visually, any shape that has four corners and four edges belongs to this family.