"... only a most die-hard literalist would insist on using agendum when talking about a single list of items to discuss." I believe "agenda", meaning "things to be acted on", has always meant the list, with each item on the list being an "agendum". What's certainly changed is that "agenda" is now treated as a singular noun.

All the little differences. What in English is called 'engagement book' we call 'agenda'. It can be a personal, business or school agenda. And a single list of items to discuss we also call 'agenda'. Agendum I have never seen used in our language.
Funny I never thought before about the real meaning of the word.
Thank you.

I agree, Bran - as a long time committee-man (on all sorts of committees!) I have never come across the use of 'agendum.' I guess you are right Trivia, that it refers to each item on the agenda. And I most certainly have fairly often come across the use of 'agendas.' I suppose it has now been used aften enough to count as being "part of the language."

Welcome, tstrivia.
AHD:
a·gen·dum (-jndm) KEY

NOUN:
pl. a·gen·da (-d) KEY also a·gen·dums
Something to be done, especially an item on a program or list.

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ETYMOLOGY:
Latin, neuter gerundive of agere, to do; see ag- in Indo-European roots