The list of subjects or problems to which governmental officials, and people outside of government closely associated with those officials, are paying some serious attention at any given time.
(Kingdon, John W, Agendas, Alternatives, and Public Policies, 2nd ed, Ann Arbor: University of Michigan Press, 1995. p3)
It is important to distinguish between the "governmental" agenda - the list of subjects that are getting attention - and the "decision" agenda - the list of subjects within the governmental agenda that are up for an active decision. Kingdon, 1995, pp. 20.
Roger Cobb et al. use different terms: the public agenda contains issues that have a high level of interest and resonance with the population, whereas the formal agenda is the list of issues that the government has officially resolved to consider.
Kingdon makes an important distinction between large scale agendas, such as the governmental agenda, and specialized agendas, such as the health care or transportation agenda. It is even within specialized agendas like health care he says, that there exists still more specialized agendas.
Cobb, Roger, Jennie Keith-Ross and Marc Howard Ross. 1976. “Agenda Building as a Comparative Political Process" American Political Science Review 70, 1, 126-38.
Kingdon, John W, Agendas, Alternatives, and Public Policies, 2nd ed, Ann Arbor: University of Michigan Press, 1995. p3