How is an angle formed in geometry?

An angle in geometry is formed when two lines or line segments meet at a common point, known as the vertex of the angle. This intersection creates space between the two lines that can be measured in degrees, which is how angles are quantified. The point at which the lines or segments converge is crucial, as it signifies the angle itself.

The dimensions of the angle are determined by the amount of rotation from one line to the other around the vertex. Understanding this concept is essential in geometry because angles are fundamental to the study of shapes, properties of triangles, and various geometric figures.

The other options describe other concepts. For instance, three points coming together can form a triangle but does not specifically create an angle, and bisecting a line segment refers to dividing it into two equal parts without involving angles. Similarly, when a line extends infinitely, it indicates a direction but does not inherently define an angle unless another line intersects it.