The word "serif" is probably derived from the Dutch schreef meaning "stroke". A serif is a short line which meets an extremity of a letter or number at an angle. For example, the capital letter A is sometimes drawn with horizontal serifs at the base of each of its "feet":
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In Roman times, when lettering was often cut into stone, masons would chisel the serif before drawing the rest of the letter, to stop the main strokes from running too far across the stone. When typography was revised during the Renaissance, Roman lettering was revisited and the serif regained popularity, although divorced from its original practical justification.
Another explanation of the serif's popularity comes from calligraphy. With non-ballpoint pens, it can be necessary to rub the tip of the pen back and forth across the paper to start the ink flowing. The resulting mark can be incorporated into the character by treating it as a serif.
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