Relative velocity (vA±vB) for two bodies A and B has both units (ms−1) and dimensions [LT−1]. Relative density of two substances (ρ=
ρA
ρB
)A and B have no units and no dimensions. Angle is measured in radian. Thus, it has units but no dimensions. Energy is measured in joule and has dimensions[ML2T−2]. Hence, only relative density has neither unit nor dimensions.