Writing or decoration in red ink.
Rubrics are the handwritten titles, chapter headings, and instructions that are not part of the original text but are added to aid the reader in identifying these elements. The term is derived from the Latin word for red, rubrica, as often, rubrications appear in red to be easily distinguished from the text.
From the Latin rubrica, red. The use of colored lines of writing were most often, but not always, written in red and served as instructional guides to the reader, providing descriptive headings and marking divisions in the text. Rubrication can also refer to the patterns of red dots often used around letterforms and decorations in Celtic illumination. Rubricated title lines Patterns of rubricated dots in the Lindisfarne Gospels
A title, chapter heading, or instruction that is not strictly part of the text but which helps to identify its components. Red ink was often used to distinguish such elements, hence the term, which derives from the Latin for red, rubrica.
Rubrication was one of several steps in the medieval process of manuscript making. Practitioners of rubrication, so-called rubricators, were specialized scribes who received text from the manuscript's original scribe and supplemented it with additional text in red ink for emphasis. The term rubrication comes from the Latin rubrico, "to color red".