(mathematics) The number G=𝛽(2)=∑ₙ₌₀ ᪲((-1)ⁿ)/((2n+1)²)=1/(1²)-1/(3²)+1/(5²)-1/(7²)+1/(9²)-⋯, where β is the Dirichlet beta function, with a value of approximately 0.915965594177…

(mathematics, chiefly historical) Synonym of pi

(mathematics, number theory) The sum of numbers in any row, column, or diagonal of a magic square.

(mathematics) The number 𝜁(3)=∑ₙ₌₁ ᪲1/(n³), where ζ is the Riemann zeta function, with a value of approximately 1.2020569…

(physics) any of a set of physical quantities that play a fundamental role in basic theories

(physics) a universal constant, R, that appears in the ideal gas law, PV=nRT, derived from two fundamental constants, the Boltzmann constant and Avogadro's number, R=N_Ak.

Alternative spelling of Hubble constant

(physics) the constant of proportionality in the equation of Coulomb's law; numerical value depends on the units used

(astronomy) A number that expresses the rate of expansion of the universe; the velocity at which a distant object is receding from the Earth divided by its distance; its reciprocal determines the age of the universe.

(physics) the constant of proportionality (symbol h), relating the energy and frequency of a photon (6.626 × 10⁻³⁴ joule-seconds); also related to the indeterminacy limit in the Heisenberg uncertainty principle; the quantum of action