Technical writing

Punctuation:

1. Length of dash : Hyphen < en dash < em dash

examples:

Hyphen: 28-year-old woman, well-established

　 en dash: Ranges of values; For ages 3–5,

Relationship and connections; Tokyo–London flight, Bose–Einstein statistics

em dash:

Hyphen and en dash are not accompanied by spaces before and after them.

For more, see https://en.wikipedia.org/wiki/Dash