The actual unit is lower case, the multiplier is uppercase.

Wouldn’t agree with that… There are many different units and multipliers. the letter being uppercase or lowercase has nothing to do with it.

Examples:

letters for prefixes/multipliers being uppercase and lowercase: P, T, G, M, k, h, da, d, c, m, u, n (trillion, billion, million, thousand, hundred, ten, one tenth, one hundredth, one thousandth, one millionth, one billionth)

Letters for units being uppercase and lowercase: s, m, g, N, W, J, A, K, V, h, Hz (seconds, meter, gram, Newton, Watt, Joule, Ampere, Kelvin, Volt, hour, Hertz) (just recognised, that most units, which are named after scientists, are written with capital letters…)

km = thousand meters/kilometer

K = Kelvin (unit for temperature)

M = Mega (prefix for one million)

kJ = thousand joules

s = second

ms = millisecond (one thousandth)

S = siemens (electrical conductivity)

mS = milli siemens

mm = millimeter (one thousandth of a meter)

Mm = megameter (one million meters or thousand kilometers)