Nu (letter)

Nu (/ˈnjuː/ ^ⓘ; uppercase Ν, lowercase ν; Greek: vι ni, [ni]) is the thirteenth letter of the Greek alphabet, representing the voiced alveolar nasal [n]. In the system of Greek numerals it has a value of 50. It is derived from the Phoenician nun . Its Latin equivalent is N, though the lowercase ( $\nu$ ) resembles the Roman lowercase v.

The name of the letter is νῦ (nû, [nŷː]) in Ancient Greek, while in Modern Greek it is νι (ni, [ni]).

Letters that arose from nu include N in the Latin script and En (Н) in Cyrillic.

Symbology

The lower-case letter $ν$ is used as a symbol in many academic fields. Uppercase nu is not used, because it appears identical to Latin N.

Mathematics:
- Degrees of freedom in statistics.
- The greatest fixed point of a function, as commonly used in the μ-calculus.
- Free names of a process, as used in the π-calculus.
- One of the Greeks in mathematical finance, known as "vega".
- The reciprocal of 1 plus the interest rate in finance.
- The $p$ -adic valuation or $p$ -adic order of a number.
Physics:
- Kinematic viscosity in fluid mechanics.^[1]
- The frequency^[2] of a wave in physics and other fields; sometimes also spatial frequency; wavenumber
- The specific volume in thermodynamics.
- Poisson's ratio, the ratio of strains perpendicular with and parallel with an applied force.
- Any of three kinds of neutrino in particle physics.
- The number of neutrons released per fission of an atom in nuclear physics.
- Molecular vibrational mode, $ν x$ where $x$ is the number of the vibration (a label).
- The true anomaly, an angular parameter that defines the position of a body moving along an orbit (see orbital elements).
Biology:
- A DNA polymerase found in higher eukaryotes and implicated in translesion synthesis.
Chemistry:
- The stoichiometric coefficient.
Psychology:
- The maximum conditioning possible for an unconditioned stimulus in the Rescorla-Wagner model.

Encodings of Greek Nu and Coptic Ni.^[3]

^ The MATHEMATICAL symbols should only be use for math. Stylized Greek text should be encoded using the normal Greek letters, with markup and formatting to indicate text style.

^ Elert, Glenn (2023), "Special Symbols", The Physics Hypertextbook, hypertextbook, retrieved 2025-02-01, ν kinematic viscosity
^ See e.g. Planck's formula
^ Unicode Code Charts: Greek and Coptic (Range: 0370-03FF)

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