The relationship between the height of a grid's lead strips to the distance between them is termed as grid:

The term that describes the relationship between the height of a grid's lead strips and the distance between them is known as the grid ratio. This ratio is important in radiography as it helps determine how effectively the grid can reduce scatter radiation while allowing the primary beam to pass through. A higher grid ratio indicates taller lead strips relative to the distance between them, which generally enhances the grid's ability to absorb scattered radiation, thus improving image quality.

While other options such as frequency, radius, and focusing distance may be relevant concepts in different contexts related to grids, they do not specifically pertain to the defined relationship between strip height and distance. Frequency, for instance, refers to how often the lead strips occur within a given area but does not directly relate to the height and spacing. Radius typically refers to a measurement related to curvature or pinpointing a central location, and focusing distance pertains to the distance at which focused rays converge, which is not the same as the grid ratio.