Symbols · Greek letters

μ Μ Mu

Say it: “mu” · MYOO (rhymes with "few")

What it means

The twelfth Greek letter. μ is the mean of a population, the prefix micro (one millionth, as in μm), a coefficient of friction and, in fluids, dynamic viscosity.

Read aloud in real formulas

Statistics

z = (x − μ) / σ

Aethel says

z equals the quantity x minus mu, over sigma

μ is the mean

Mechanics

F = μN

Aethel says

F equals mu N

friction is μ times the normal force

Typing it

LaTeX: \mu (capital: M)
Unicode: U+03BC, U+039C

Formulas that use it

Variance

σ² = (1/n) ∑ᵢ (xᵢ − μ)²

z-score

z = (x − μ) / σ

Normal distribution

f(x) = (1 / (σ√(2π))) e^(−(x − μ)² / (2σ²))

Navier–Stokes equation

ρ(∂u/∂t + u · ∇u) = −∇p + μ∇²u + f

Questions

How do you pronounce mu (μ)?

It is said “mu”, roughly MYOO (rhymes with "few").

What does μ mean in maths?

The twelfth Greek letter. μ is the mean of a population, the prefix micro (one millionth, as in μm), a coefficient of friction and, in fluids, dynamic viscosity.

How do you type μ?

In LaTeX, write \mu (capital: M). Its Unicode code point is U+03BC, U+039C.

What is μ often confused with?

It is easy to mistake for u, and the micro sign µ (U+00B5), which looks the same.