Minkowski metric tensor in relativity η-conversion in lambda calculus the learning rate in machine learning and statistics Θθ (theta) Θ (uppercase) represents: an asymptotically tight bound related to big O notation. sensitivity to the passage of time in mathematical finance in set theory, a certain ordinal number (lowercase) represents: a plane angle in geometry the angle to the x axis in the xy-plane in spherical or cylindrical coordinates (mathematics) the angle to the z axis in spherical coordinates (physics) the potential temperature in thermodynamics theta functions the angle of a scattered photon during a Compton scattering interaction the angular displacement of a particle rotating about an axis the Watterson estimator in population genetics ("script theta"), the cursive form of theta, often used in handwriting, represents the first Chebyshev function in number theory Ιι (iota) represents: an inclusion map in set theory the index generator function in APL (in the form ⍳) the imaginary number equal to square root of −1 the interior product Κκ (kappa) Κ represents: the Kappa number, indicating lignin content in pulp represents: the Von Kármán constant, describing the velocity profile of turbulent flow the kappa curve, a two-dimensional algebraic curve the condition number of a matrix in numerical analysis the connectivity of a graph in graph theory curvature dielectric constant thermal conductivity (usually a lowercase Latin ) electrical conductivity of a solution thermal diffusivity a spring constant (usually a lowercase Latin ) the heat capacity ratio in thermodynamics (usually ) the receptor which dynorphins have the highest affinity for in pharmacology Λλ (lambda) Λ represents: the Lebesgue constant (interpolation), a bound for the interpolation error the von Mangoldt function in number theory the set of logical axioms in the axiomatic method of logical deduction in first-order logic the cosmological constant the lambda baryon a diagonal matrix of eigenvalues in linear algebra a lattice molar conductivity in electrochemistry represents: one wavelength of electromagnetic radiation the decay constant in radioactivity function expressions in the lambda calculus a general eigenvalue in linear algebra the expected number of occurrences in a Poisson distribution in probability the arrival rate in queueing theory the failure rate in reliability engineering the Lagrange multiplier in mathematical optimization, known as the shadow price in economics the Lebesgue measure denotes the volume or measure of a Lebesgue measurable set longitude in geodesy linear density ecliptic longitude in astronomy the Liouville function in number theory the Carmichael