In typography, serifs are the small features at the end of strokes within letters. A typeface (font) without serifs is called sans-serif (from French sans: "without"), also referred to as grotesque (or, in German, grotesk).

In the Roman alphabet, serifs originated with the carving of words into stone in ancient Italy. Artisans would carve out a bit of extra space at the end of the long strokes of letters in order to prevent gravel and dust from collecting in the corners of the letters.

For more on typeface classification, see the "typeface" article.

The etymology of "serif" is obscure, but in any case almost as recent as the face. The oldest citations in the Oxford English Dictionary are 1841 for sans serif, which the OED gives as sanserif, and 1830 for serif. Indeed, the OED speculates that serif was a back-formation from sanserif. On the other hand, Webster's Third New International Dictionary traces serif to the Dutch schreef meaning "stroke", and ultimately through German schreiben and Latin scribere, both also meaning "to write".

The OED's earliest citation for grotesque in this sense is 1875, giving "stone-letter" as a synonym. It would seem to mean "out of the ordinary" in this usage, as in art grotesque usually means "elaborately decorated". Other synonyms include Doric and Gothic.

San Serriffe is an elaborate typographically related joke.

Typically serif fonts are used for body text because the serifs tend to guide the eye along the line, while sans serif fonts are used for headings and for small sections of text, because they typically look 'cleaner' to the eye.