Alan Peake wrote:
"V/I has dimensions of resistance - ratios are dimensionless."

Yes, until we name them. Cycles / seconds is now called Hertz.

My electronics dictionary defines ratio -
"The value obtained by dividing one number by another."

Simple and no qualifications.

From Newton:
Acceleration = force / mass

You must pick the right units or use constants to make the numbers work.

Some people are persuaded that resistance = loss. Not so at all.
Resistance is just a name given to the ratio of voltage to current. A
perfect reactance produces a voltage drop but no power is lost. A
transmission line can be lossless enough to qualify and have a Zo = sq
rt of L/C. Reg Edwards used to say that if your perfect line were long
enough you could measure its Zo with an ohmmeter. Reg was right because
no reflection would ever return to change the current supplied by the
ohmmeter.

Free-space has a lossless Zo of 120 pi (or 377 ohms) according to page
326 of Saveskie`s "Radio Propagation Handbook". This is a ratio which is
related to volts and amps but is actually the ratio of the electric
field strength to the magnetic field strength in an EM wave. The volts
and amps are in phase so it has the units of a pure resistance.

Best regards, Richard Harrison, KB5WZI