A class or category:"This mission is sometimes discussed under the rubric of 'horizontal escalation'. . from conventional to nuclear war"(Jack Beatty). A title; a name.
A part of a manuscript or book, such as a title, heading, or initial letter, that appears in decorative red lettering or is otherwise distinguished from the rest of the text.
A title or heading of a statute or chapter in a code of law.
Ecclesiastical A direction in a missal, hymnal, or other liturgical book.
An authoritative rule or direction.
A short commentary or explanation covering a broad subject.