My proofreader recently revealed to me the following, which I was wholly unaware of:

...when a number/code/serial or whatever is said in dialogue, you write the whole thing out...

I had written the designation of a robot as Unit M55/987.3, and he said I would need to sound it out:

...“Unit Em-fifty-five slash nine hundred eighty-seven-point-three has been terminated.”...

Is this true? If it is true, can I still 'ignore' it as one of those grammatical liberties authors sometimes take (in the same class as using fragments)?


3 Answers 3


In fiction, there's no rule for this, only differing styles and opinions. However, some editors seem to like using the Chicago Manual of Style's alternative rule for this.

9.3 An alternative rule--zero through nine. Many publications, including those in scientific or journalistic contexts, follow the simple rule of spelling out only single-digit numbers and using numerals for all others [...]

It goes on to reference the exceptions to this. (9.3 is an alternative to the more strict rule 9.2 that requires spelling out all numerals from zero through one hundred.)

Exceptions to these include spelling out round numbers. For example: "seven hundred", "one thousand", "forty-seven thousand", etc. There are also other rules for money, ordinal numbers, decimals, percentages, etc, but these are overkill for fiction.

The number you indicate in your question is more like a serial number. I can't find anything for that, but personally I'd use the abbreviated rule for numerals in general, using numerals and letters and not spelling them out. Unless the character's name were something short like the robots in Star Wars, where (for example) R2-D2 becomes "Artoo" for short.

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    I'd like to add that I despise applying CMOS to fiction unilaterally, but it seems to be depressingly common. Commented Apr 2, 2015 at 21:26
  • So it will probably be fine if I just write numbers/serials as M55/987.3? Could a publisher have a problem with that, or could I still get it through without revising it? Commented Apr 2, 2015 at 22:57
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    @TommyMyron I'd use the digits and letters for this example. Writing out the words for such a long item seems ridiculous. Commented Apr 3, 2015 at 10:00
  • @TommyMyron Revised my answer to clarify. Commented Apr 5, 2015 at 3:49

Neil's answer does not really deal with dialogue. Style manuals like the Chicago Manual of Style deal with academic and journalistic writing. If you want to apply them to narrative fiction, they only apply to that part of your writing that is explicitly in written language, that is, everything outside the dialogue. Dialogue is spoken language, or rather, dialogue in narrative fiction is the written emulation of spoken language, and it follows its own rules and styles.

To answer your question:

Dialogue is what people say. You do not say "9", but "nine". Therefore, in dialogue, you should write "nine".

This can become cumbersome to read, if long strings of numbers and/or letters are repeated often in dialogue. In this case the string becomes common and can be treated like common abbreviations (e.g. BMW or UK), which readers perceive as words and which therefore are represented in written dialogue in their word-form, not in their sound-form.

In your case your proofreader is right if that designation of a robot is said only once. If, like C3PO, it is used as a name-like handle to repeadedly talk about the robot, you should use the number-form instead.

If I was writing this story, my chaeacter would read M55/987.3 as: "fifty-five, nine eighty-seven, three".

My character wouldn't speak the slash and dot, in the same way an American saying a price does not say "three comma fifty". And he would not say the M either, because there is no 55/987.3 in any other series. You migjt say "three dollar fifty", but you need not, because it is the only currency in Ohio. If he'd have to refer to this robot often, he would call it "the fifty-five". That would serve as a name-like handle. He would only spell out the whole serial number if he was unfamiliar with the robot -- but then it would not be a name, because a name is a familiar word.


My character would say "fifty-five" in the same way that I don't say "Samsung Galaxy S III LTE I9305".

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    It is used only once - but it is used as a name. The robot is promptly destroyed before it can be used again. However, I always found "See-threepio" or "artoo" extremely jarring when I read it, which is why I think numbers/letters work far better. Commented Apr 3, 2015 at 17:34
  • @TommyMyron If it is used as a name, no one would say it in full. See my edit.
    – user5645
    Commented Apr 3, 2015 at 21:59
  • What if you needed everything? What if you needed the slash, dot, and M? It's not in my tale, but in the unknown backstory, there's an M class, a DW class, an O class, so on. There could easily be two M55/987.3's in two different classes. Similarly, there could be a M5/598.73. Writing it out 'M55/987.3' might look a little weird in dialogue, sure, but wouldn't it be far stranger/potentially more confusing if you say it a different way than normal, and leave parts out? Commented Apr 3, 2015 at 23:28
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    @TommyMyron I can only repeat myself. In the end you will have to decide what feels best for you. We have given you everything you need to decide. Is that designation familiar to the reader? If not, it is not a name to him but a random string of numbers that he does not know how to pronounce. Does that matter? etc. It's your book. We told you what we would do, and there obviously is no one correct way to do this, so yoi need to weigh the different arguments and decide what is most important to you: visual ease or spoken language. In the end it will be a minor element ;-)
    – user5645
    Commented Apr 4, 2015 at 7:01

Arguably, one could say that the pronunciation of such a string is ambiguous. Would someone say it "em five five slash nine eight seven dot three" or "em fifty-five nine eighty-seven point three" or other possible variations. If the "M" stands for something, do they say the word or just the letter "M"? Etc. If it matters in the story, then you need to spell it out. Like if there's a scene where someone is saying the serial number but doesn't get a chance to finish before the transmission line is cut or whatever, and then the person hearing says "well, it's a nine-hundred series, that at least narrows it down", but if he said "nine eight ..." rather than "nine hundred eighty ...", how does the hearer know that the number had three digits and not 2 or 4? Or if the "M" stands for, I don't know, "Mercury", and you just give it as "M55" and the reader says it in his head as "em five five", and then later a character who is unfamiliar with these serial numbers asks, "Is that related to the planet Mercury, the element, or the Greek god?" the reader may wonder, Wait, how did he know that "M" stands for "Mercury". And then maybe he'll say, Oh, I've been reading it wrong, George must have been saying "Mercury five five", not "em five five". Etc. That is, you don't want to leave a pronunciation ambiguous, let the reader pick one plausible pronunciation in his head, and then three chapters later say something that indicates that he's been reading it wrong all this time, and now he has to re-interpret scenes he's already read.

But if none of that matters, if it's just an identifier, and whether the reader says it in his head one way or the other makes no difference at all, then I'd think giving it in a short form is better, because it's more compact. If the reader says it in his head differently than you were thinking when you were writing it, but it doesn't matter, so what?

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    An excellent breakdown. Unless the name has some sort of meaning that can't be conveyed just by letters/numbers, I don't see any reason to sound it out. In my experience, that jars heavily against the reader. Commented Apr 3, 2015 at 17:36

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