I'm charged with translating a technical document into English, and ran into a bit of an odd problem: the document refers to undefined numbers of elements, and uses letters to represent those numbers, as you would see in algebra. The order of those elements are important, so they need to be written as ordinal numbers.

In the source language (Japanese), an ordinal number is denoted with the character "第" (dai), so "第1" becomes "first", "第2" becomes "second", and so on. But how should I translate "第s"? "Nth" is common in English to refer to an undefined degree, but "rth" or "sth" seems confusing to me. Unfortunately, uppercase and lowercase letters are defined as different numbers, so I can't simply capitalize.

Is there a convention for this? Should I add a hyphen e.g. "s-th", or enclose the letter in parenthesis e.g. "(s)th"?

  • Why can't you use "nth"? Another option, if you already are using "nth" is "kth".
    – Laurel
    Apr 26, 2018 at 1:33
  • I pretty much have to use the variables as defined in the source text, which are "N", "n", "r", and "s". Altering those would make things confusing for the author of the specification, and would involve altering a lot of diagrams as well.
    – ahawkins82
    Apr 26, 2018 at 1:39

1 Answer 1


Use italics for mathematical variables. Nth or rth. You can also sometimes see superscripts, Nth or rth.

  • I would prefer not to use superscripts, but I think italicizing the variables would be the way to go.
    – ahawkins82
    Apr 26, 2018 at 1:41

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