(geometry) A special number associated with an ordered quadruple of collinear points, particularly points on a projective line, and preserved by the fractional linear transformations.

(biology, sociology) The ratio of males to females in any given population.

(philosophy) “Right reason”, which regards virtue as desirable in itself.

(measurement, statistics) A scale of measurement of data having a fixed zero value, which permits the quantitative comparison of differences of values.

(physics, mathematics) A dimensionless measure of the damping in second-order linear dynamic system, appearing as the term 𝜁 in the generalised equation of motion for such a system, ̈q+2𝜁𝜔ₙ̇q+𝜔ₙ²q=F.

(geography) The number of people under the age of 15 and over the age of 64 compared to the number of people active in the labor force.

(chemistry) The ratio of the percent of one enantiomer in a mixture to that of the other

Abbreviation of price-earnings ratio.

(philosophy, logic) the formal grounds for something; the essential attributes of matter as they appear in the mind or in a definition.

(finance) A ratio that measures the excess return (or risk premium) per unit of deviation in an investment asset or a trading strategy, used to examine the performance of an investment by adjusting for its risk.