Agenda is the gerundive neuter plural of the verb agere. It means "what must be done." In English we treat is as a singular, rather than distinguishing between agendum and agenda. An agenda or research project is the overarching context of a scholar's profile. "Writing three articles" is not an agenda in the sense I mean: that's just a list of three things to do.
My research agenda is to better the state of poetry criticism in my field (modern, contemporary Peninsular literature) by relating it to larger intellectuals trends in intellectual and cultural history; to trace the genealogy of the late modern movement in contemporary Spain; to integrate the contribution of Lorca into modern Spanish poetry in a more convincing way.
I would have defined my agenda differently five years ago, or ten years ago, or fifteen, or twenty. Some parts have remained constant, but my interests have shifted. I've always had a clear sense of my agenda, however.