A minus symbol, rather than a hyphen, is used in text to show a negative quantity or subtraction:
−20 °C a − b = c
Caution! Do not use a hyphen in place of a minus symbol.
Insert the minus symbol in Word from the symbol set (mathematical operators; unicode 2212). In some fonts, it sits slightly higher than the en dash and has slightly more space around it.
However, it is also acceptable to use an en dash (but not a hyphen) to represent the minus sign.
Caution! Some screen readers do not read en dashes and minus signs correctly. Not all screen readers behave the same: some may ignore the proper minus sign, whereas others may read a hyphen as a minus sign when it is before a number. If accessibility is important, try to experiment with screen readers.