M3 stands for Motorsport 3-series, a high-performance version of the 3-series. Most M3 parts are interchangeable with the non-M models, and you may find parts with either the M3 logo or the M logo on non-M models.
It stands for "Motorsports" Audi has the S Mercedes has the AMG BMW has the M
m3 can mean m x 3 i do not know what m stands for. Most likely mass or motion. It depends on the given information. When a variable(a letter) is next to a number, that means you multiply them.
m3 + 1 = (m + 1)(m2 - m + 1)
"m cube" is m3.
The M in the Greek alphabet is "upper case" Mu.
m3*m5 = m3+5 = m8
Mezzazine
m3*m5 = m3+5 = m8
If the 3 is raised, it means m to the third power. If it's a measurement, it may mean cubic meters.
Moisture
m3