Rules of thumb for written abbreviations

Here's something that might interest you CPFers, since we talk about volts, watts, milliamps, milliamp-hours and such... rules I've followed as a professional technical writer in my work, but never fully realized why.

When terms come from a proper name, we spell them out in lowercase. 10 volts, 20 newton-meters... Rudolph Diesel invented it, but it's a diesel engine. When abbreviating, we use the uppercase. 10 V, 20 Nm, etc.

Ampere, Volt, Watt, Weber... all people's names.

How about kilo, mega, giga...? The rules are a bit hazier here. Usually, milli and kilo are abbreviated with a lowercase "m" and "k" respectively. It's a 10 kW dummy load or an LED that requires 100 mA of current. Micro is abbreviated with the Greek letter mu, or µ. Some engineers make a super-big deal about not using a lowercase "u" instead, and insist on the usage of mu. Some don't give a rat's butt either way.

Millisecond = ms
Microsecond = µs

Mega and giga are uppercase. 10 MW carbon-arc light haha. Or 10 GW carbon arc light if you're feeling fancy.

So how about "milliamp-hour"? The only word that is derived from a name is Ampere. So it would be abbreviated mAh.

Miles per hour = mph, all-wheel drive = awd and so on and on and on hahaha...

That's my imponderable for the day.

EDIT: I forgot one, "decibel." It's abbreviated dB because a "Bel" is the base unit of measurement. According to this article on Wikipedia:

"A decibel is one tenth of a bel (B (approximately 1.6 km) length of standard ). Devised by engineers of the Bell Telephone Laboratory to quantify the reduction in audio level over a 1 miletelephone cable, the bel was originally called the transmission unit or TU, but was renamed in 1923 or 1924 in honor of the Bell System's founder and telecommunications pioneer Alexander Graham Bell. In many situations, however, the bel proved inconveniently large, so the decibel has become more common."

It's been my understanding that prefixes representing quantities greater than one or zero begin with a capital letter, quantities smaler than one are lower case. As a matter of respect, I capitalize terms derived from proper names and common units are lower case.
Kilo gram=1000 grams
Mega Volt= 1,000,000 Volts
centi meter (usually one word) = 1/10 meter
milli meter= 1/1000 meter.
milli Amp= 1/1000 Amp
Call me nuts or whatever name you choose, just the way I do things.

The SI system has fixed rules for abbreviations and capitalization ( Wiki entry for SI as starting point). And lower and uppercase letters DO mean different units. Example: "g" is the unit for mass (though the SI base unit is the kg), "G" (Gauss) is a unit for magnetic field (though the official SI unit is Tesla, T). That was a big problem within the cgs system, that physicists used before the introduction of SI, since g and G are proper units in this system (cgs = centimeter, gram, seconds instead of m, kg, s). SI tries to avoid confusion of this magnitude, though.

The "µ" is another pet peeve of mine. If I can't find it in a hurry, I type "micro". "u" is the atomic mass unit.

Yes, the official abbreviation for "milli Ampere hours" is "mAh". And currents are measured in Amperes, abbreviated "A". As a professional (I'm a physicist) it drives me nuts if those rules are not observed .

Prefixes: 10^6 (M, mega) and above are capitalized, below that they're lowercase ("µ" is a lowercase letter, the uppercase mu looks like "M"). "Kilo" = 10^3 = 1000 is abbreviated "k", not "K". Why? Because "K" is the symbol for temperature unit, Kelvin . So, for me as a physicist, "Kg" means "Kelvin gram". Though I usually get what's meant, since there's not much measured in "Kelvin gram". Still bugs me, though.

[derail] In the cgs system, you could write all kinds of units with the three base units. Electric charge could be measured in "√(g·cm³/s²)", and current in "√(g·cm³/s^4)". Resistance is "s/cm" -- that's right, seconds per centimeter. That's why the system is still used sometimes for theoretical electrodynamics, for instance, since it makes equations easier [/derail]

Pretty much the only unit I know of that can be both abbreviated upper- and lowercase is the liter. The uppercase is primarily used in the US, to avoid confusion with (handwritten) "1"s.

And "kph" parallel to "mph" is a BIG no-no. It's language derived. Correct in written language is "km/h".

The way I've always done it is:

mA = milliamps
A = amps
mV = millivolts
V = volts
MV = megavolts
mW = milliwatts
W = watts
MW = megawatts
nm = nanometer
µm = micrometer
mm = millimeter
cm = centimeter
m = meter
µF = microfarads
F = farads
mph = miles per hour

elgarak said:

The "µ" is another pet peeve of mine. If I can't find it in a hurry, I type "micro". "u" is the atomic mass unit.

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Elgarak, interesting and informative post overall. I'm glad I'm not the only one who's weird about abbreviations. ;-)

"µ" is easily typed out from the keyboard. Hold down the ALT key and hit 0181 on the 10-key pad. Release the ALT key and µ appears.

That's for a PC, it's probably different on a Mac. If you Google "ASCII codes" you can find charts for ALT key combinations that type up the special characters. I keep a chart of commonly used characters pinned to my cubicle wall at work.

Now I'm going to finish some TÜV acceptance paperwork (ALT 154), heh...

I have a "scratch pad" file I keep open on my computer all the time; the very top line contains special characters (£ µ Å ° ¢ ÿ — ö Ö ¥ © ® ñ ¼ ½ ¾ ™© ®), so when I need to use one, I just highlight the one I need, hit CTRL-C, go to the document I'm typing, and press CTRL-V.
And viola. The special character magically appears. :thumbsup:
Easier than trying to remember the ALT-codes associated with every one.

Well, our current work is some notches below µm ... Nano is the current buzz word. So I don't have much use for µ. I use nm more... or even Å (ALT+0197)... except when I have to deal with our machine shop for building things, then I have to switch to " and mils :green: ... ahhh, zee adwentures of a German in oo ess aahh, ja!

elgarak said:

Correct in written language is "km/h".

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Wouldn't that be km·h-1?

Long live SI!! Down with this feet-inches per bushel acre nonsense! :sick2:

Hey, a fellow technical writer! That's awesome! I recently got an AA in tech writing. It's really made me appreciate clear prose.

Don't forget about 8b (eight bits) in 1B (one byte).

Interesting info from you all. I think I've been doing it mostly right, except I have to admit I do usually use a small v for volts, which from what I read above is v incorrect, lol.

Is it wrong to use lm for lumens? And how would you write bulb lumens and torch lumens?

DM51 said:

Is it wrong to use lm for lumens? And how would you write bulb lumens and torch lumens?

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According to my U.S. Government Printing Office style manual, "lm" is the correct abbreviation for lumens, but it doesn't have listings for lamp lumens or torch lumens. The same manual states that a lowercase "b" stands for "bit" (thanks Tigerhawk, heh) or "barn," and an uppercase B stands for Bel. Soooooo.... we'll have to make up our own CPF writer's style guide, LOL.

If such a guide is created, I'll be happy to make the page and host it on my website. :thumbsup:

Ok, web page is now up!!! :thumbsup:
I had to make a graphic for the " " symbol because I could not get it to display in my HTML editor or browser.

(Edit, a short time later): I just figured out how to get the "" symbol to display, so I could dispense with the graphic and make all of the symbols themselves in bold text on this web page. :twothumbs