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Metric names are sometimes abbreviated, e.g. Kilogram as kilo, megabyte as mega and nanosecond as nano.

Is it correct to add an "s" as suffix to the plural form of abbreviations?

For example:

The total weight is 10 kilo.

(as kilo is here an abbreviation of kilograms)

OR

The total weight is 10 kilos

Note: The questions is restricted to the abbreviations, not the metric symbols. It's clear to me that symbols like km (for kilometers), s (for seconds), etc. do not end with 's' in plural.


EDIT

The first comments and answers here brought to my attention that 'mega' and 'nano' are not really common abbreviations. Moreover, they are probably incorrect. I'm sure I've heard them already, but it's possible that it was always from non-native speakers like me. Correct common abbreviations (besides "kilo" for "kilogram") are "meg" for "megabytes" and "gig" for "gigabytes".

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I've seen "kilos" used for kilograms, but that's all. I've never seen "mega" or "nano" used as an abbreviation for any measurement. –  Matt Hamilton Sep 4 '10 at 17:23
    
The NOAD reports kilos as plural of kilo, but it doesn't report megas as plural of mega. –  kiamlaluno Sep 4 '10 at 17:24
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@Bruno: Can you cite an example where these abbreviations (other than kilo) are used? Perhaps that would help in answering the question. I for one have never seen "nano" and "mega" written. –  Neil Fein Sep 4 '10 at 17:28
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I haven't seen 'mega' as the abbreviation, but I've heard MB pronounced as both 'meg' and 'megs'. –  J.T. Grimes Sep 4 '10 at 17:37
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There is also the mil for milliliter and, less commonly millimeter, e.g. ten mils, twenty-five mils. –  Jimi Oke Dec 21 '10 at 23:37

5 Answers 5

up vote 6 down vote accepted

I am only familiar with the abbreviation of kilogram as kilo, and this is indeed pluralized as kilos. I have heard mega and megas from foreigners but they strike me as ungrammatical, as does nano from nanosecond (why not for nanometer?). Here’s what I found in the Corpus of Contemporary American English:

All the incidences of nanos were references to one of the following:

  • iPod nano
  • A surname Nanos
  • In science fiction, references to something like nanorobots

So, nano(s) is not a commonly-used abbreviated form for nanosecond (or nanometer)

As for megas, the only examples in COCA were three uses as a name, and one use in science fiction:

So after the Port dome went up they built this lean-to partial dome that tilts up against the Port dome like a crescent cupping a bigger arc: the Curve. It was supposed to be just warehouses and megas, not living space, so they didn't attach it to the Port dome very well and now the Curve pulls away from the Port dome a little more every year, and a little more gas and garbage falls into the Curve but nobody seems to give a damn.

It’s unclear from even this much context what a mega is, but I’m pretty sure it’s not a megabyte.

I checked also for uses of gigas for gigabytes but all the gigas in COCA are species names, where it presumably means “very large”: Strombus gigas (a sea snail), Crassostrea gigas (an oyster), Angelica gigas (a flowering plant).

So, in conclusion, don’t use mega as an abbreviation for megabyte. I understand this is common in some languages, such as Spanish, but it is not used in English. Use instead MB as the abbreviation for megabyte. However, kilo for kilogram is perfectly idiomatic, although in American English, the things most often measured in kilos are cocaine and heroin. The top 10 most common collocates for kilo are: cocaine, hundred, per, five, heroin, fifty, weighed, pounds, ten, and half.

EDIT: as pointed out in the question’s comments, meg(s) and gig(s) are the common used spoken abbreviations for megabyte(s) and gigabyte(s).

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Well to be honest kilo for kilogram technically makes just as much sense as nano for nanosecond. It could well mean kilosecond or pretty much a thousand of anything. –  Swizec Teller Dec 22 '10 at 2:06
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The way these things develop so rarely make any sense though, don't they? –  nohat Dec 22 '10 at 18:37

As the New Oxford American Dictionary reports, kilo is a noun used as abbreviation of kilogram and, rarely, of kilometer.
The same is not true for mega, which is not used as noun.
Nano is informally used as a noun, to mean nanotechnology.

Looking for nanos and megas in the Corpus of Contemporary American English I found that

  • nanos is used more in fiction, and in the newspapers; in the last case, in all the cases they are referring to the iPod Nano.

  • megas is used in fiction (It was supposed to be just warehouses and megas, not living space, so they didn't attach it to the Port dome […].), and magazines and newspapers; in the last case, the sentences make reference to the last name of a person (Mr. Megas).

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I see we were looking at the same thing at the same time ;-) –  nohat Sep 4 '10 at 17:39
    
I learned from you to look for a word in the Corpus of Contemporary American English. :-) (I don't know why, but I don't like to use the abbreviated name of the site.) –  kiamlaluno Sep 4 '10 at 18:11
    
probably because it makes more sense for the abbreviated form to be CCAE, although that is admittedly much less catchy than COCA. –  nohat Sep 7 '10 at 0:03
    
@nohat: Actually, the reason is more "botanic". :-) –  kiamlaluno Feb 23 '11 at 1:34

Both with and without the 's' seems to be common.

I buy 20 kilos of cement. It comes in a 20 kilo bag.

In Australia, the abbreviation for kilometre tends to be 'k'. One does a 5 K run. Sydney is a thousand Ks away from Melbourne.

Another common abreviation is mill, short for millimetre. From common use, it can be used with or without an 's'. There is a 5 mill gap. Draw a line 5 mills long.

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"Mill" (or "mil") can also be used as an abbreviation for millilitre, but in any event it is only used in spoken English, since in writing it is always quicker and clearer to use "mm" or "ml". –  Brian Nixon Dec 21 '10 at 23:41
    
Arguably, mill (and K) are more slang than an abbreviation. Along the lines of 'click' meaning kilometres. –  dave Dec 22 '10 at 0:25

All of these words are prefixes for engineering notation, a form of scientific notation used to represent numbers to the most significant magnitude group of ten to the power of a multiple of three - all derived from appropriate greek words.

kilo- is perhaps the most commonly encountered so the plural kilos is in common use, whereas the others are not so much. As the other prefixes are encountered more, they are coming in to use, megs, gigs, teras - these large numbers coming in via space storage in computing making them mainstream.

The smaller units do not seem to have spawned the same usage. micros has a use independent of its prefix, as the word micro has an alternative meaning; perhaps this clash prevents the use. I have heard nanos used in science fiction to refer to nanoscopic robots, otherwise it has not been adapted yet.

Theoretically all the plurals are valid for derivation in the long term, it just takes time for the words to be accepted in the mainstream.

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"Micron" is used as an abbreviation of "micrometre". –  Brian Nixon Dec 21 '10 at 23:47
    
@Brian Nixon: Quite right, microns being an acceptable plural. Interesting how the magnitude gets bound to the most common use-case for it, as with kilos implying mass. –  Orbling Dec 21 '10 at 23:55
    
I've often heard the value of a 4.7μF capacitor pronounced "four point seven mike", and 22pF pronounced "22pF". A value of 47nF would be "point oh four seven mike". –  supercat Aug 28 at 22:11

I would suggest that the term "kilo" is a unit of mass equal to 1kg. Although it is derived from "kilogram", it should be regarded as a unit of mass rather than as a term for a thousand of something. Likewise "meg" and "gig", are terms for roughly one million, and one billion bytes, respectively, as opposed to those quantities of everything else. The term "K" (pronounced "k") generally refers to 1,024 bytes, but may sometimes be used to refer to $1,000, or it may be used with a discrete item to indicate quantity (e.g. we need 50K fully-assembled units by next July).

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