A more thorough explanation:

Definition: Incidental, adjective. Subordinate to something of greater importance; having a minor role.

Example: The broken pencil was incidental to the student's success on the test.

Explanation: In this example, the broken pencil is not the main focus or cause of the student's success on the test. It is a minor detail that is not as important as other factors, such as studying or understanding the material.

Example: The color of the walls was incidental to the overall design of the room.

Explanation: In this example, the color of the walls is not the main focus or purpose of the room's design. It is a minor detail that does not have as much importance as other design elements, such as furniture or lighting.