The "inclination of a plane" refers to the angle at which a flat surface, or plane, is tilted relative to a horizontal surface. This angle is often measured in degrees and can affect various physical properties, such as the distribution of weight and the movement of objects on the surface. In engineering and architecture, understanding the inclination of a plane is crucial for designing structures like ramps and roofs. The angle can influence factors such as drainage, stability, and accessibility, making it an important consideration in construction and design projects.