In typography, an all-inclusive term for characters that have a line crossing the free end of a stroke. The term serif refers to both that finishing line, and to characters and typefaces that have them.
It is said that the Romans invented the serif as a solution to the technical problem of getting a chisel to cut a neat, clean end to a character. Later, it became an emulation of handwriting, with flat "pens" producing thick and thin curves, based on the angle of the pen.
Serif characters tend to be easier to read, as they provide a horizontal guideline for the eye to "tie" the letters of a word together. It is generally better to use serif faces (rather than sans serif faces) when typesetting long stretches of copy, such as books with few illustrations, since serif faces cause less fatigue of the eyes. According to one study, there is reader preference for, and better legibility of, serif faces. Half-serifs on horizontal arms are sometimes called beaks, and serifs at the end of arcs are called barbs. A character exhibiting a curvature of the transition from the main stroke to the serif is referred to as bracketed. A character in which the angle from the main stroke to the serif is a right angle is described as square serif. See also Sans Serif.