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If you have a quantity of items, where the items themselves are described with a measurement, how should you format this so it is unambiguous?

For example, This diagram contains...

  • two hundred thirty-five millimeter circles. (looks like you have 235 circles)
  • 200 35mm circles. (only a space prevents it from being over twenty thousand circles)
  • 200× 35mm circles. (looks like the circles are somehow 200mm × 35mm)
  • 200 - 35mm circles. (looks like 200 minus 35)

A good solution needs to work for various numbers: 200 35mm circles, 129 2.5mm circles, etc.

Joe
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    200 35-mm circles – JLG Dec 17 '12 at 17:43
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    You forgot two hundred 35mm circles. – Jim Dec 17 '12 at 17:55
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    @JLG A hyphen is not correct when dealing with metric measurements, although it may be acceptable with Imperial units. – Andrew Leach Dec 17 '12 at 18:15
  • Where is this sentence to appear? "This diagram contains 200 circles 35mm ø" would work in some circumstances, but not all. [That should ideally be a diameter symbol] – Andrew Leach Dec 17 '12 at 18:18
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    Related: How do I write consecutive numbers and How to write numbers one after the other in different context. – Hellion Dec 17 '12 at 18:51
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    @WayfaringStranger Subscript is the wrong term. They're called old style numerals as opposed to lining numerals you may be more familiar with. – spiceyokooko Dec 17 '12 at 19:42
  • @AndrewLeach, Then 200 35-millimeter circles, but that's actually a matter of style. We use hyphens with metric units all of the time. – JLG Dec 17 '12 at 19:49
  • I think the links supplied by @Hellion make this not just a duplicate, but a merge candidate. Though I am open to merging the older questions into this one rather than the other way round. – RegDwigнt Dec 18 '12 at 10:52
  • @RegDwighт, I suggest closing as a duplicate, rather than merging. I searched this site for all the ways I could think to ask this question -- if someone else searches using the same terms I did, they'd rather see a closed-as-duplicate question than miss the question entirely. – Joe Dec 18 '12 at 14:47
  • @Joe: merging does leave up all of the questions involved. It merely transfers all answers (and comments) from question X to question Y. But question X is still left as a signpost, pointing to question Y using a different wording. It is not deleted. In other words, merging is identical to closing as duplicate in every regard, except that all answers are conveniently collected in one place. What I'm putting up for debate here is what place that should be — this right here, this, or this. – RegDwigнt Dec 18 '12 at 15:17
  • @RegDwighт, in that case, I'd say to merge the answers to this question. I think the title is the most accurate of the three at describing the problem. – Joe Dec 18 '12 at 15:51

2 Answers2

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According to the SI system (guide here: http://physics.nist.gov/cuu/pdf/sp811.pdf), acceptable options are

  • 200 35 mm circles,
  • 200 35-millimeter circles,
  • 200 circles of 35 mm diameter.

The pertinent rules from the guide above are:

7.2. Space between numerical value and unit symbol

In the expression for the value of a quantity, the unit symbol is placed after the numerical value and a space is left between the numerical value and the unit symbol.

The only exceptions to this rule are for the unit symbols for degree, minute, and second for plane angle: º, ', and ", respectively (see Table 6), in which case no space is left between the numerical value and the unit symbol.

This rule means that:

(a) The symbol ºC for the degree Celsius is preceded by a space when one expresses the values of Celsius temperatures.

(b) Even when the value of a quantity is used as an adjective, a space is left between the numerical value and the unit symbol. (This rule recognizes that unit symbols are not like ordinary words or abbreviations but are mathematical entities, and that the value of a quantity should be expressed in a way that is as independent of language as possible—sees Secs. 7.6 and 7.10.3.)

However, if there is any ambiguity, the words should be rearranged accordingly. For example, the statement “the samples were placed in 22 mL vials” should be replaced with the statement “the samples were placed in vials of volume 22 mL.”

Note: When unit names are spelled out, the normal rules of English apply. Thus, for example, “a roll of 35-millimeter film” is acceptable (see Sec. 7.6, note 3).

and

10.5.3. Grouping digits

Because the comma is widely used as the decimal marker outside the United States, it should not be used to separate digits into groups of three. Instead, digits should be separated into groups of three, counting from the decimal marker towards the left and right, by the use of a thin, fixed space. However, this practice is not usually followed for numbers having only four digits on either side of the decimal marker except when uniformity in a table is desired.

Here's a worse case: "20 350 mm circles". In this case, there is still no problem, but the distinction would be very subtle:

  • A small space between "20" and "350" means 20350, while a large space means 20 of the 350 mm circles.
  • The context may distinguish a bunch of small circles or one big circle.
David Smith
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200 of 35mm circles, 129 of 2.5mm circles, ...

This format can easily suggest an elision of numbers without much effort on the part of the reader: 200 (numbers) of 35mm circles, 129 (numbers) of 2.5mm circles, ...

Considering this is ELU, I presume you are asking about a part of a full grammatical sentence, not a caption/ title.

Kris
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