Dimensionless numbers

measure of inequality in income or wealth distribution

thumb|400px|right|Several sets of (x, y) points, with the Pearson correlation coefficient of x and y for each set. The correlation reflects the noisiness and direction of a linear relationship (top row), but not the slope of that relationship (middle), nor many aspects of nonlinear relationships (bottom). N.B.: the figure in the center has a slope of 0 but in that case, the correlation coefficient is undefined because the variance of Y is zero.

inverse function of the trigonometric function

The way to measure the hardness of a material is with a special tool called an indenter, which is pressed into the material and the larger the cavity, the harder the material.

difference in luminance and/or color that makes objects visually distinguishable

set of pseudo units to describe small values of miscellaneous dimensionless quantities

ratio of an aircraft's wing span to its mean chord

dimensionless quantity that characterizes plant canopies

capacity utilization of public transport