Vertex:
The common end point where two rays meet to form an angle is called the vertex. It is the point where the two rays intersect or come together. The vertex is represented by a dot and is usually labeled with a letter.

Explanation:
When two rays intersect, they form an angle. An angle is a geometric figure formed by two rays with a common endpoint. The endpoint is known as the vertex. It is the starting point for measuring the angle.

Example:
Let's consider two rays, Ray AB and Ray AC. When these two rays meet at point A, they form an angle. In this case, point A is the vertex of the angle.

Importance of the Vertex:
The vertex is an essential part of an angle as it helps in identifying and measuring the angle accurately. Without the vertex, angles cannot be defined or understood properly.

Properties of the Vertex:
1. The vertex is a point.
2. It is the common endpoint of the two rays forming the angle.
3. The vertex is represented by a dot and is usually labeled with a letter.
4. The vertex does not have any length, width, or thickness.

Conclusion:
In geometry, the common end point where two rays meet to form an angle is called the vertex. It is important to understand the concept of the vertex in order to accurately define and measure angles. The vertex is a point and is represented by a dot, usually labeled with a letter.