μ | mu

The Greek letter μ (mu) arose from the ancient Phoenician letter 𐤌 (mēm) which, in turn, was derived from the Egyptian hieroglyph for water, 𓈖.

The lower-case μ has many uses in maths, engineering and sciences, for example:

• in coordination chemistry: μ-, a prefix for a bridging ligand
• in electromagnetism:
  • the magnetic moment and the units to express it, such as the Bohr magneton μ_B and the nuclear magneton μ_N
  • the permeability µ, measured in henries per meter (H·m⁻¹);
  • the vacuum permeability or magnetic constant µ₀, which has the exact value of 4π×10⁻⁷ H·m⁻¹
• in fluid mechanics: dynamic viscosity
• in mathematics: the Möbius function μ(n)
• in maths and physics: µ (micro-), a unit prefix in the metric system for 10⁻⁶ (one millionth)
• in particle physics: muon μ⁻ and antimuuon μ⁺ (formerly called μ-mesons)
• in pharmacology: μ-opioid receptor (MOR)
• in physics: the coefficient of friction
• in physics: the electrical_mobility of a charged particle
• in thermodynamics: chemical potential aka partial molar free energy μ_i

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