(1) A stroke added to the beginning or the end of one of the main strokes of a letter. In the roman alphabet, serifs are usually reflexive finishing strokes, forming unilateral or bilateral stops. (They are unilateral if they project only to one side of the main stroke, like the serifs at the head of T and the foot of L, and bilateral if they project to both sides, like the serifs at the foot of T and the head of L.) Transitive serifs — smooth entry or exit strokes — are the norm in italic. There are many descriptive terms for serifs, especially as they have developed in roman faces. They may be not only unilateral or bilateral, but also long or short, thick or thin, pointed or blunt, abrupt or adnate, horizontal or vertical or oblique, tapered, triangular and so on. In blackletters they are frequently scutulate (diamond shaped), and in some script faces, such as Tekton, the serifs are virtually round. (Not all type historians agree that the word serif should be used in the relation to italic letters. But some term is is necessary to denote the difference between, for example, Bembo italic and Gil Sans italic. The former is described as a serified italic, the latter as unserified).
See also a picture of serif styles
(2) The name of typefaces with serifs. See Antiqua.
See also Serif Typefaces in Classification section.