In various contexts, μ represents different things. Here are some of the meanings of μ:

• Greek letter: μ is the twelfth letter of the Greek alphabet, representing the voiced bilabial nasal. In the system of Greek numerals, it has a value of 40).
• Metric prefix: "μ" is used as a unit prefix denoting a factor of 10−6 (one millionth), in this context, the symbol its name is "micro".
• Symbol in mathematics: "μ" is conventionally used to denote certain things in mathematics, such as a measure in measure theory, minimalization in computability theory and Recursion theory, the integrating factor in ordinary differential equations, and the degree of membership in a fuzzy set).
• Symbol in physics: In physics, the letter μ is commonly used to represent the coefficient of friction and magnetic permeability. The designation μ0 (pronounced as mu naught or mu zero) refers to the permeability of free space. It is also known as the permeability of vacuum and the magnetic constant.
• Population mean in statistics: The Greek letter μ (mu) is used in statistics to represent the population mean of a distribution.

It is important to note that the lowercase letter μ is used as a special symbol in many academic fields, while uppercase mu is not used because it appears identical to Latin M).