Scallop shell
A good real life example of polygon is a scallop shell. The polygon formed in the above figure is 16-sided. Can you identify the number of diagonals from the vertex A and the total number of diagonals possible?
A closed plane figure bounded by three or more line segments is called a polygon.
The line segments forming a polygon are called its sides and the point
of intersection of two consecutive sides of a polygon is called a vertex.
The number of vertices of a polygon is equal to the number of its sides.

**Diagonal of a polygon:** A line segment joining any two
non–consecutive vertices of a polygon is called its
diagonal. Thus, in the above figure, ABCDEF is a polygon and each of the line
segments AC, AD, AE, BD, BE, BF, CE, CF and DF is a diagonal of the polygon.

The number of diagonals from any one vertex for a 'n' sided polygon is given by: (n – 3). Isn't it?