The point where the sides of a polygon meet is called the vertex. A polygon is a closed plane figure with three or more sides.
Any polygon has as many vertices as it does sides. This applies to both convex as well as concave polygons. Even the diagonals meet in the vertex of the polygon.
For instance, a triangle is a three-sided polygon, and it has three vertices. A quadrilateral is a four-sided polygon, and it has four vertices. A rectangle, a square, a rhombus, a parallelogram and a trapezium are polygons with four sides and four vertices.
A hexagon and a heptagon have six and seven sides, respectively. A hexagon has six vertices, and a heptagon has seven.