Definition
Em dash
An em dash (—) is a dash the width of the type size, used to mark a break in a sentence or an interrupted line of dialogue. It is the longest of the three horizontal marks.
Style traditions differ and a book should pick one and hold it: US publishing generally sets the em dash closed up to the words either side, while UK practice often uses a spaced en dash instead. Two typesetting consequences follow. A closed-up em dash creates a long unbreakable run, which in a narrow measure forces loose lines; and a line should not begin with a dash, so a break before one usually needs repairing.
Related tools & guides
See it handled in your own manuscript
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