halfem

Halfem, or half-em, is a typographic unit representing half the width of an em. An em is the width of the current font size, so a halfem scales with the font. In typography, the halfem concept can refer to a half-em space—a horizontal space whose width is half an em—or, less commonly, to a halfem dash, a punctuation length shorter than an en dash but longer than a hyphen.

Usage today is rare; designers may rely on 0.5em values in digital layout for precise spacing, or rely on standard punctuation marks and kerning to achieve the desired effect. Some font families and legacy typesetting systems historically used halfem measures to fine-tune justification and alignment that were not achievable with the more widely used en and em spaces.

Because the em width varies with font size, halfem measurements also scale, making layout responsive across sizes. There is no universally standardized glyph for a halfem dash in Unicode; when needed, designers generally emulate it with the available dash characters or adjust spacing.