The degree of inclination of a slope, road, or other surface.
A grouping of organisms done purely on the basis of shared features and without regard to evolutionary relationships. Grades may include organisms that do not share a common ancestor, or may exclude some organisms having the same common ancestor as the other organisms in the grade. For this reason, many taxonomists do not accept grades as formal classifications. The class Reptilia (reptiles) is a grade since it includes dinosaurs but not birds, even though birds are descended from dinosaurs. Compare clade.