What does em mean?
"Em" is the name of the thirteenth letter of the English alphabet, M, pronounced /ɛm/. Beyond its role as a letter name, em carries a specialized meaning in typography: it denotes a unit of measurement equal to the size of the type being set, so a 12-point em measures 12 points across. This unit underlies several familiar terms, including the em dash (a long punctuation mark), the em space, and the em quad, all of which take their dimensions from this standard. Because an em scales with the type size rather than being fixed, it allows designers to specify proportional spacing that remains consistent across different fonts and sizes. The word appears most often in professional publishing, design, and editing contexts, while its everyday use is limited to spelling out or referring to the letter itself.
The name of the letter M.
"Write a capital Em at the start of the sentence."
Usually capitalized when referring to the letter.
A unit of measurement in typography equal to the point size of the current type.
"Indent the paragraph by one em."
Typically used in plural form ('ems') in professional typesetting contexts.
Applies mainly to the typographic unit sense; the letter-name sense is usually treated as an uncountable reference to the letter itself.
"The layout called for two ems of space between sections."
In typography, an em isn't tied to the width of the letter M at all — it's simply whatever the font's point size happens to be, so an em grows and shrinks with your text.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of em
As the name of the letter M, "em" descends through Middle English and Old French from Latin "em," the Roman name for the letter M, which itself derives from the Semitic letter mem via Greek mu. The typographic sense arose in early modern printing, when metal type was cast on bodies roughly the width of the capital M, giving printers a convenient unit named after that letter.
How em is actually used
As a letter name it is usually capitalized ('Em'). The typographic sense appears mostly in professional publishing contexts, typically pluralized as 'ems'. Informally, 'em' is also a casual spoken rendering of the pronoun 'them', but that colloquial use is best treated separately from the dictionary senses above.
Easily confused with em
An 'en' is the letter N and, typographically, half the width of an em — hence an en dash is shorter than an em dash.