Final answer:
A solid angle is the angle formed by the junction of three surfaces at one point, distinct from a contact angle which involves a liquid surface.
Step-by-step explanation:
An angle formed by the junction of three surfaces at one point is called the solid angle. Unlike the contact angle, which is the angle formed between the tangent of a liquid surface and another surface, a solid angle is a three-dimensional equivalent of the planar angles we usually measure in degrees or radians. A good example of a solid angle could be seen at the corners of a cube, where three planes (each of a face of the cube) meet at one vertex and form an angle in three-dimensional space.