Time for another blog post where I try to improve science grammar.
This is the lower case Greek letter mu: μ. This is the lower case Latin letter u: u. Latin letters are, of course, what are used in the English alphabet as well as many, many other languages. While μ and u look similar, they are different. The Greek letter mu, uppercase Μ, is closer to the Latin letter M. The Latin letter U (uppercase, or u, lowercase) is more related to the Greek letter Upsilon (uppercase Υ, lowercase υ).
So now that I got that out of the way, when it comes to science in particular, μ and u are NOT interchangeable. In the International System of Units (SI), otherwise known as the Metric system, μ is the symbol used to represent the prefix micro-. “μ” can easily be added into a document using a insert symbol compound. It is an easy procedure, and there is no need to be lazy and just use “u”. “u” does not mean micro-. It is wrong. Don’t do it.