that subtends the arc of a circular curve in surveying the maximum degree of any vertex in a given graph sensitivity to price in mathematical finance the discriminant of a polynomial (in a quadratic polynomial determines the nature of the roots) represents: percent error a variation in the calculus of variations the Kronecker delta function the Feigenbaum constants the force of interest in mathematical finance the Dirac delta function the receptor which enkephalins have the highest affinity for in pharmacology the Skorokhod integral in Malliavin calculus, a subfield of stochastic analysis the minimum degree of any vertex in a given graph a partial charge. δ− represents a negative partial charge, and δ+ represents a positive partial charge chemistry (See also: Solvation) the chemical shift of an atomic nucleus in NMR spectroscopy. For protons, this is relative to tetramethylsilane = 0. stable isotope compositions declination in astronomy noncentrality measure in statistics The transition function in the formal definition of a finite automaton, pushdown automaton, or Turing machine Not to be confused with ∂ which is based on the Latin letter d but often called a "script delta." Εε (epsilon) represents: a small positive quantity; see limit a random error in regression analysis the absolute value of an error in set theory, the limit ordinal of the sequence in computer science, the empty string the Levi-Civita symbol in electromagnetics, dielectric permittivity emissivity strain in continuum mechanics permittivity the Earth's axial tilt in astronomy elasticity in economics electromotive force in chemistry, the molar extinction coefficient of a chromophore in mathematics, a surreal number that is bigger than zero, but smaller than all the non-negative numbers. set membership symbol ∈ is based on ε (digamma) is sometimes used to represent the digamma function, though the Latin letter F (which is nearly identical) is usually substituted. A hypothetical particle Ϝ speculated to be implicated in the 750 GeV diphoton excess, now known to be simply a statistical anomaly Ζζ (zeta) represents: the Riemann zeta function and other zeta functions in mathematics the damping ratio Ηη (eta) Η represents: the Eta function of Ludwig Boltzmann's H-theorem ("Eta" theorem), in statistical mechanics Information theoretic (Shannon) entropy represents: the intrinsic wave impedance of a medium (e.g. the impedance of free space) the partial regression coefficient in statistics, also interpreted as an effect size measure for analyses of variance the eta meson viscosity energy conversion efficiency efficiency (physics) the