The en dash

This is for the real experts! Most native English speakers don't know this.

The en dash (–) is a symbol you can't find on most keyboards. It is longer than the hyphen (-) and shorter than the em dash (—). It is called en dash because it is as wide as a capital en (N).

The en dash is used to indicate a range of numbers, e.g. 70–80 g/L.

The en dash is also used to contrast two words, like solid–liquid separation, the gas–liquid interface and the London–Paris flight.

Note that compound adjectives like liquid-soap dispenser or small-scale fermentation, where the first adjective modifies the second adjective (i.e. the soap is liquid and the scale is small), are written with a normal hyphen (see previous article).
 

More information on this sexy punctuation can be found here.