What is the meaning of μ?

(Should we delete this sense?) micro-

population mean

coefficient of friction

magnetic permeability

muon

Standard gravitational parameter

micron

Lower-case mu (μῦ), the 12th letter of the ancient Greek alphabet. It represented the bilabial nasal /m/. It is preceded by λ and followed by ν.

The lower case letter mu (μι), the 12th letter of the modern Greek alphabet.

meter (metre), the unit of length in the International System of Units

Source: wiktionary.org