Any of a set of parameters for a quasi-experimental model used to describe the directional reflectance properties of the airless regolith surfaces of bodies in the Solar System.

(statistics) A parameter of the distribution of a population that is not directly relevant to solving the significance test or estimate problem under consideration.

(relativity) speed divided by the speed of light, symbol β

(programming) a parameter that is passed by position, rather than by name, in a function call

(programming) a parameter that is passed by name, rather than by position, in a function call

(physics) A dimensionless quantity, denoted by η, used in nuclear astrophysics in the calculation of reaction rates between two nuclei and in the definition of the astrophysical S-factor.