In statistics, the t-distribution is important. It is an approximation to the normal distribution. Of course we don't say "normal-distribution" (with the dash).

Well then, what exactly is the grammatical justification for calling it


as opposed to just

t distribution


Or to put it another way, is there a good name for the practice of using a dash in this kind of context?

  • single letters alone are considered ugly? (except for 'I' and 'a' (unless those are just the letters and not the single-letter words))
    – Mitch
    Commented Dec 13, 2018 at 0:09
  • 2
    These types of things are jargon of the field, they're often ideosyncratic.
    – Barmar
    Commented Dec 13, 2018 at 0:39

1 Answer 1


A hyphen — not a dash — commonly joins an initial single letter/digit to form a compound word [Public Works and Government Services_Canada ... BtB Translation Bureau].

Left to its own devices, general usage will capitalize:

A-side, B-side, T-shirt, A-shirt, O-level, X-ray

Otherwise, various commercial or scientific fields set their own conventions. There is no particular reason why, for instance, it's t-distribution but T-cell beyond the tendency in mathematics not to capitalize letters except in special circumstances. In other words, it’s E = mc2 by community agreement and convention.

Many e-words such as e-commerce, e-learning, and especially e-mail are dropping their hyphens. I've also seen B movie both ways.

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