An em dash sets off an amplifying or explanatory element, separates a subject or series of subjects, or indicates a sudden break in thought or sentence structure: We will fly to Paris — if I get a raise. Put a space before and after the em dash, which is an exception to Chicago style. Do not use a pair of hyphens to create an em dash. see also en dashes, hyphens, and CMS 6.82–6.89