Rubric was the name applied to those portions of old manuscripts and books which, for typographical embellishment or on account of their importance in the text, were printed in red ink. Often, as in the old monastic manuscripts, only initial letters in the paragraph were so treated. With the development of the copyist's art, however, rubified manuscripts became ornate; the initial letter of every noun, perhaps, was rubricated, chapter headings, thumb-nail indexes, marginal comments, and in cases whole passages of the text were highly ornamented rubrics.
The use of the red letter text became common w. the case of religious treatises, and so certain rules and directions in prayer books, explanations and responses are printed in red ink. This is the case with the Roman missal, where the matins, lauds, beatifications, etc., are always in red, and in the liturgy, where the directions for the performance of the service are also in red. In the old Bibles the chapter heads were so treated. Modern typography discards such profuse use of colored ink and usually substitutes in its place type of a different face from the rest of the text, but the portions thus emphasized are still called rubrics.
Spanish custom has given another significance to the word, and in Spanish denotes the flourish so common after Spanish signatures. This likewise results from the fact that the rubrics were the most conspicuous features of a page.