I have no idea if this is meterhertz or millihertz
nHz is Nanohertz 1/1,000,000,000 Hz (Billionth)
µHz is Microhertz 1/1,000,000 Hz (Millionth)
mHZ is Millihertz 1/1,000 Hz (Thousandth)
Hz is Hertz 1 Hz (Base Unit, one per second)
kHz is Kilohertz 1,000 Hz (Thousand)
MHz is Megahertz 1,000,000 Hz (Million)
GHz is Gigahertz 1,000,000,000 Hz (Billion)
THz is Terahertz 1,000,000,000,000 Hz (Trillion)
I suppose there are probably more that I’m not aware of, but I hope this clears it up.
No, that absolutely does not resolve the confusion between meter (m) and milli (m)
No one uses millihertz and neither meterhertz. If you want to do it correctly the first one would be acceptable for milli as scale. The second one would need to be written as
m • Hz.Millihertz are used for gravitational waves in Astrophysics.
