(1) Magisterial or priestly: a board of officials. (2) Private: any private association of fixed membership and constitution (see clubs, roman).The principle of collegiality was a standard feature of republican magistracies at Rome. Although in some cases the common status of colleagues did not exclude seniority (originally one *consul may have been superior to the other and the consuls as a whole were senior colleagues of the *praetors), the principle in general was to avoid arbitrary power by ensuring that every magistracy should be filled by at least two officials, and in any case by an even number. They were to possess equal and co-ordinate authority, but subject to mutual control. Thus a decision taken by one consul was legal only if it did not incur the veto (*intercessio) of the other. This principle led to alternation in the exercise of power by the consuls each month. Under the Principate emperors might take as a colleague in their tribunician power (see tribuni plebis) their intended successors, who in many cases were co-emperors.