I'm translating some software from German (where there's a correct way for everything) into English (my native language, but also where I do so much more just by feeling) and I'm stumped by things like:

T value
X coordinate
Y coordinate

My sense is that all three should not be hyphenated or capitalized (though I'm not sure about at the beginning of a sentence.) I should have made it more clear in writing the original question that I'm talking about capitalizing the words 'value' or 'coordinate.'

Some examples (not real, but of the sort I'd have to translate) might be:

  • Transform T value
  • X value out of range
  • Enter Y coordinate

Just recently the topic came up with my boss and she asked if that was the rule in English and I truthfully told her I didn't know. Is it the rule? Is there a rule?

  • Frankly, that line says next to nothing, "T value X coordinate Y coordinate" you will need to provide full context. In the given field of technical writing, T & t do not mean the same, for instance. Even less can be said about hyphenation without the full context.
    – Kris
    Dec 20, 2013 at 13:45
  • @Kris: I added some examples. So far, I'm translating the interface to the program, so there aren't many subject-verb-object sentences. Dec 20, 2013 at 20:35
  • @Peter: Can I take it to mean that T-value is hyphenated? Dec 20, 2013 at 20:36

1 Answer 1


This isn't German; there is no rule. This isn't covered by English grammar, but by the conventions of whatever field of science/engineering you are writing in.

In the fields of math, physics, and computer science, the ones I am familiar with, the question is whether the variable you are talking about is named x or X.

If it's named x, you never capitalize it, not even at the beginning of a sentence. And you try not to start a sentence with it.

If it's named X, you always capitalize it (and you still try not to start a sentence with it).

From Google Ngrams, it looks like people use both upper- and lowercase letters for all three of these quantities, although t-value is usually lowercase.

  • I edited the question to try to make it more clear. I'm asking about capitalizing the words 'value' or 'coordinate' following the T, X, Y, or Z (which, by convention, are always capitalized in the company that produces the software) And it looks, by the way people are writing, that I can say that only T-value is hyphenated? Dec 20, 2013 at 20:42
  • The 'c' and 'v' in $X$ coordinate and $T$-value should not be capitalized, even at the beginning of a sentence. I would capitalize "T-Value" in a chapter title, but I think it depends on your general rule for words with hyphens; in a chapter title, would you use "Forty-two" or "Forty-Two"? Dec 20, 2013 at 22:59

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