noun, formally a plural of, agendum but usually used as a singular with plural, agendas or agenda.
a list, plan, outline, or the like, of things to be done, matters to be acted or voted upon, etc.:
The chairman says we have a lengthy agenda this afternoon.
1745-55; < Latin, plural of agendum that which is to be done, gerund of agere to do; the plural orig. carried a collective sense denoting the various items to be transacted
Agenda, “things to be done,” is the plural of the Latin gerund agendum and is used today in the sense “a plan or list of matters to be acted upon.” In that sense it is treated as a singular noun; its plural is usually agendas: The agenda is ready for distribution. The agendas of last year's meetings are printed in the official minutes. The singular agendum, meaning “an item on an agenda,” is rare.
1650s, from L., lit. "things to be done," from neut. pl. of agendum, gerundive of agere (see act). Originally theological (opposed to matters of belief), sense of "items of business to be done at a meeting" first attested 1882.