A hyphen is not a minus sign, and other mistaken characters

Several characters are simply short horizontal lines: the hyphen -, the minus sign −, the en dash –, and the em dash —. Each has a specific purpose, but often the hyphen is used regardless. This is bad practice.

The dash is not the only culprit; various other characters are incorrectly used. Typically these relate to mathematics or scientific quantities.

Character Purpose Bad replacement
Minus Subtraction, negative Hyphen
Times × Multiplication Letter ‘x’ or asterisk x, *
Prime Minutes (angle) Apostrophe
Ellipsis Continuation Three periods . . .
Thin space 1 m Precede unit Normal space 1 m
En dash Denote range Hyphen
Plus–minus ± Uncertainty Plus–slash–minus +/−
Arrow Direction Dash–greater than –>

Consider 1.2 × 10−2 K m−1 versus 1.2 x 10-2 K m-1 (times not x, minuses not hyphens, thin not standard spaces before and between units). You might argue that the latter form is sufficient because the reader knows exactly what is meant. That’s true, but the same can be said for misspelled words and bad grammar. Many people spend a lot of time ensuring correct spelling and grammar, but ignore the correct use of symbols.

Why use the wrong symbols?

There are three likely reasons you would use the incorrect symbols. First, you don’t realise there is a difference. Second, the wrong symbols are output by an application you are using (e.g., Matlab exports figures with hyphens instead of minus signs for negative numbers). Third, the incorrect symbol is on the keyboard, so you use that instead.

By reading until here you’ve overcome the first problem. Overcoming the second problem is unfortunately beyond the scope of this post. So consider the last problem. If the desired symbol is not on the keyboard, adding it can be a pain. For example, (i) go to Character Map or Unicode Lookup, (ii) find the desired symbol, (iii) copy, (iv) return to the application being used, and (v) paste.

There’s no need to repeat the find-copy-paste process every time. Head over to Add any symbol without leaving the keyboard to find out how to add symbols quickly.

Author: Ken Hughes

Post-doctoral research scientist in physical oceanography

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